Merge branch 'master' into tokens-payment

# Conflicts:
#	src/backend/taler-merchant-httpd_private-post-orders.c
#	src/backenddb/Makefile.am
#	src/backenddb/merchant-0006.sql
#	src/backenddb/pg_insert_token_family_key.c

83 files changed, 3884 insertions, 685 deletions

diff --git a/src/backend/Makefile.am b/src/backend/Makefile.am
index dbc7cde8..cce7faec 100644
--- a/src/backend/Makefile.am
+++ b/src/backend/Makefile.am
@@ -37,6 +37,8 @@ taler_merchant_httpd_SOURCES = \
     taler-merchant-httpd_mhd.h \
   taler-merchant-httpd_private-delete-account-ID.c \
     taler-merchant-httpd_private-delete-account-ID.h \
+  taler-merchant-httpd_private-delete-categories-ID.c \
+    taler-merchant-httpd_private-delete-categories-ID.h \
   taler-merchant-httpd_private-delete-instances-ID.c \
     taler-merchant-httpd_private-delete-instances-ID.h \
   taler-merchant-httpd_private-delete-instances-ID-token.c \
@@ -59,12 +61,18 @@ taler_merchant_httpd_SOURCES = \
     taler-merchant-httpd_private-get-accounts.h \
   taler-merchant-httpd_private-get-accounts-ID.c \
     taler-merchant-httpd_private-get-accounts-ID.h \
+  taler-merchant-httpd_private-get-categories.c \
+    taler-merchant-httpd_private-get-categories.h \
+  taler-merchant-httpd_private-get-categories-ID.c \
+    taler-merchant-httpd_private-get-categories-ID.h \
   taler-merchant-httpd_private-get-instances.c \
     taler-merchant-httpd_private-get-instances.h \
   taler-merchant-httpd_private-get-instances-ID.c \
     taler-merchant-httpd_private-get-instances-ID.h \
   taler-merchant-httpd_private-get-instances-ID-kyc.c \
     taler-merchant-httpd_private-get-instances-ID-kyc.h \
+  taler-merchant-httpd_private-get-pos.c \
+    taler-merchant-httpd_private-get-pos.h \
   taler-merchant-httpd_private-get-products.c \
     taler-merchant-httpd_private-get-products.h \
   taler-merchant-httpd_private-get-products-ID.c \
@@ -93,6 +101,8 @@ taler_merchant_httpd_SOURCES = \
     taler-merchant-httpd_private-get-webhooks-ID.h \
   taler-merchant-httpd_private-patch-accounts-ID.c \
     taler-merchant-httpd_private-patch-accounts-ID.h \
+  taler-merchant-httpd_private-patch-categories-ID.c \
+    taler-merchant-httpd_private-patch-categories-ID.h \
   taler-merchant-httpd_private-patch-instances-ID.c \
     taler-merchant-httpd_private-patch-instances-ID.h \
   taler-merchant-httpd_private-patch-orders-ID-forget.c \
@@ -109,6 +119,8 @@ taler_merchant_httpd_SOURCES = \
     taler-merchant-httpd_private-patch-webhooks-ID.h \
   taler-merchant-httpd_private-post-account.c \
     taler-merchant-httpd_private-post-account.h \
+  taler-merchant-httpd_private-post-categories.c \
+    taler-merchant-httpd_private-post-categories.h \
   taler-merchant-httpd_private-post-instances.c \
     taler-merchant-httpd_private-post-instances.h \
   taler-merchant-httpd_private-post-instances-ID-auth.c \
diff --git a/src/backend/taler-merchant-exchange.c b/src/backend/taler-merchant-exchange.c
index 7945cb50..72566e9b 100644
--- a/src/backend/taler-merchant-exchange.c
+++ b/src/backend/taler-merchant-exchange.c
@@ -32,8 +32,8 @@
  * long-polling and do not want to wake up too often.
  */
 #define EXCHANGE_TIMEOUT GNUNET_TIME_relative_multiply ( \
-    GNUNET_TIME_UNIT_MINUTES, \
-    30)
+          GNUNET_TIME_UNIT_MINUTES, \
+          30)
 
 /**
  * How many inquiries do we process concurrently at most.
@@ -1154,7 +1154,8 @@ find_work (void *cls)
       return;
     }
     GNUNET_log (GNUNET_ERROR_TYPE_INFO,
-                "No open inquiries found, waiting for notification to resume\n");
+                "No open inquiries found, waiting for notification to resume\n")
+    ;
   }
 }
 
@@ -1215,7 +1216,7 @@ run (void *cls,
   {
     GNUNET_break (0);
     GNUNET_SCHEDULER_shutdown ();
-    global_ret = EXIT_NO_RESTART;
+    global_ret = EXIT_FAILURE;
     return;
   }
   if (NULL ==
@@ -1233,7 +1234,7 @@ run (void *cls,
     GNUNET_log (GNUNET_ERROR_TYPE_ERROR,
                 "Failed to connect to database\n");
     GNUNET_SCHEDULER_shutdown ();
-    global_ret = EXIT_NO_RESTART;
+    global_ret = EXIT_FAILURE;
     return;
   }
   {
diff --git a/src/backend/taler-merchant-httpd.c b/src/backend/taler-merchant-httpd.c
index 95ba9bf1..a7c1cbb4 100644
--- a/src/backend/taler-merchant-httpd.c
+++ b/src/backend/taler-merchant-httpd.c
@@ -34,6 +34,7 @@
 #include "taler-merchant-httpd_get-templates-ID.h"
 #include "taler-merchant-httpd_mhd.h"
 #include "taler-merchant-httpd_private-delete-account-ID.h"
+#include "taler-merchant-httpd_private-delete-categories-ID.h"
 #include "taler-merchant-httpd_private-delete-instances-ID.h"
 #include "taler-merchant-httpd_private-delete-instances-ID-token.h"
 #include "taler-merchant-httpd_private-delete-products-ID.h"
@@ -45,9 +46,12 @@
 #include "taler-merchant-httpd_private-delete-webhooks-ID.h"
 #include "taler-merchant-httpd_private-get-accounts.h"
 #include "taler-merchant-httpd_private-get-accounts-ID.h"
+#include "taler-merchant-httpd_private-get-categories.h"
+#include "taler-merchant-httpd_private-get-categories-ID.h"
 #include "taler-merchant-httpd_private-get-instances.h"
 #include "taler-merchant-httpd_private-get-instances-ID.h"
 #include "taler-merchant-httpd_private-get-instances-ID-kyc.h"
+#include "taler-merchant-httpd_private-get-pos.h"
 #include "taler-merchant-httpd_private-get-products.h"
 #include "taler-merchant-httpd_private-get-products-ID.h"
 #include "taler-merchant-httpd_private-get-orders.h"
@@ -62,6 +66,7 @@
 #include "taler-merchant-httpd_private-get-webhooks.h"
 #include "taler-merchant-httpd_private-get-webhooks-ID.h"
 #include "taler-merchant-httpd_private-patch-accounts-ID.h"
+#include "taler-merchant-httpd_private-patch-categories-ID.h"
 #include "taler-merchant-httpd_private-patch-instances-ID.h"
 #include "taler-merchant-httpd_private-patch-orders-ID-forget.h"
 #include "taler-merchant-httpd_private-patch-otp-devices-ID.h"
@@ -70,6 +75,7 @@
 #include "taler-merchant-httpd_private-patch-token-families-SLUG.h"
 #include "taler-merchant-httpd_private-patch-webhooks-ID.h"
 #include "taler-merchant-httpd_private-post-account.h"
+#include "taler-merchant-httpd_private-post-categories.h"
 #include "taler-merchant-httpd_private-post-instances.h"
 #include "taler-merchant-httpd_private-post-instances-ID-auth.h"
 #include "taler-merchant-httpd_private-post-instances-ID-token.h"
@@ -932,6 +938,52 @@ url_handler (void *cls,
       .method = MHD_HTTP_METHOD_GET,
       .handler = &TMH_private_get_instances_ID_kyc,
     },
+    /* GET /pos: */
+    {
+      .url_prefix = "/pos",
+      .method = MHD_HTTP_METHOD_GET,
+      .handler = &TMH_private_get_pos
+    },
+    /* GET /categories: */
+    {
+      .url_prefix = "/categories",
+      .method = MHD_HTTP_METHOD_GET,
+      .handler = &TMH_private_get_categories
+    },
+    /* POST /categories: */
+    {
+      .url_prefix = "/categories",
+      .method = MHD_HTTP_METHOD_POST,
+      .handler = &TMH_private_post_categories,
+      /* allow category data of up to 8 kb, that should be plenty */
+      .max_upload = 1024 * 8
+    },
+    /* GET /categories/$ID: */
+    {
+      .url_prefix = "/categories/",
+      .method = MHD_HTTP_METHOD_GET,
+      .have_id_segment = true,
+      .allow_deleted_instance = true,
+      .handler = &TMH_private_get_categories_ID
+    },
+    /* DELETE /categories/$ID: */
+    {
+      .url_prefix = "/categories/",
+      .method = MHD_HTTP_METHOD_DELETE,
+      .have_id_segment = true,
+      .allow_deleted_instance = true,
+      .handler = &TMH_private_delete_categories_ID
+    },
+    /* PATCH /categories/$ID/: */
+    {
+      .url_prefix = "/categories/",
+      .method = MHD_HTTP_METHOD_PATCH,
+      .have_id_segment = true,
+      .allow_deleted_instance = true,
+      .handler = &TMH_private_patch_categories_ID,
+      /* allow category data of up to 8 kb, that should be plenty */
+      .max_upload = 1024 * 8
+    },
     /* GET /products: */
     {
       .url_prefix = "/products",
@@ -949,7 +1001,7 @@ url_handler (void *cls,
          in the code... */
       .max_upload = 1024 * 1024 * 8
     },
-    /* GET /products/$ID/: */
+    /* GET /products/$ID: */
     {
       .url_prefix = "/products/",
       .method = MHD_HTTP_METHOD_GET,
diff --git a/src/backend/taler-merchant-httpd_config.c b/src/backend/taler-merchant-httpd_config.c
index 3777904f..10f0cd39 100644
--- a/src/backend/taler-merchant-httpd_config.c
+++ b/src/backend/taler-merchant-httpd_config.c
@@ -42,7 +42,7 @@
  * #MERCHANT_PROTOCOL_CURRENT and #MERCHANT_PROTOCOL_AGE in
  * merchant_api_config.c!
  */
-#define MERCHANT_PROTOCOL_VERSION "14:0:10"
+#define MERCHANT_PROTOCOL_VERSION "16:0:12"
 
 
 /**
@@ -82,14 +82,20 @@ MH_handler_config (struct TMH_RequestHandler *rh,
                    struct TMH_HandlerContext *hc)
 {
   static struct MHD_Response *response;
+  static struct GNUNET_TIME_Absolute a;
 
   (void) rh;
   (void) hc;
+  if ( (GNUNET_TIME_absolute_is_past (a)) &&
+       (NULL != response) )
+  {
+    MHD_destroy_response (response);
+    response = NULL;
+  }
   if (NULL == response)
   {
     json_t *specs = json_object ();
     json_t *exchanges = json_array ();
-    struct GNUNET_TIME_Absolute a;
     struct GNUNET_TIME_Timestamp km;
     char dat[128];
 
diff --git a/src/backend/taler-merchant-httpd_contract.h b/src/backend/taler-merchant-httpd_contract.h
index 006d0205..6389cc70 100644
--- a/src/backend/taler-merchant-httpd_contract.h
+++ b/src/backend/taler-merchant-httpd_contract.h
@@ -367,7 +367,7 @@ struct TALER_MerchantContractTokenFamily
 };
 
 /**
- * Struct to hold contract terms in v0 and v1 format. v0 contracts are mdoelled
+ * Struct to hold contract terms in v0 and v1 format. v0 contracts are modelled
  * as a v1 contract with a single choice and no inputs and outputs. Use the
  * version field to explicitly differentiate between v0 and v1 contracts.
  */
diff --git a/src/backend/taler-merchant-httpd_mhd.c b/src/backend/taler-merchant-httpd_mhd.c
index e96acca5..0bb22b35 100644
--- a/src/backend/taler-merchant-httpd_mhd.c
+++ b/src/backend/taler-merchant-httpd_mhd.c
@@ -59,6 +59,7 @@ TMH_MHD_test_html_desired (struct MHD_Connection *connection)
   bool ret = false;
   const char *accept;
 
+  // FIXME: use TALER_MHD_check_accept here!
   accept = MHD_lookup_connection_value (connection,
                                         MHD_HEADER_KIND,
                                         MHD_HTTP_HEADER_ACCEPT);
diff --git a/src/backend/taler-merchant-httpd_private-delete-categories-ID.c b/src/backend/taler-merchant-httpd_private-delete-categories-ID.c
new file mode 100644
index 00000000..892dbd9c
--- /dev/null
+++ b/src/backend/taler-merchant-httpd_private-delete-categories-ID.c
@@ -0,0 +1,92 @@
+/*
+  This file is part of TALER
+  (C) 2024 Taler Systems SA
+
+  TALER is free software; you can redistribute it and/or modify it under the
+  terms of the GNU Affero General Public License as published by the Free Software
+  Foundation; either version 3, or (at your option) any later version.
+
+  TALER is distributed in the hope that it will be useful, but WITHOUT ANY
+  WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR
+  A PARTICULAR PURPOSE.  See the GNU General Public License for more details.
+
+  You should have received a copy of the GNU General Public License along with
+  TALER; see the file COPYING.  If not, see <http://www.gnu.org/licenses/>
+*/
+/**
+ * @file taler-merchant-httpd_private-delete-categories-ID.c
+ * @brief implement DELETE /private/categories/$ID
+ * @author Christian Grothoff
+ */
+#include "platform.h"
+#include "taler-merchant-httpd_private-delete-categories-ID.h"
+#include <taler/taler_json_lib.h>
+
+
+/**
+ * Handle a DELETE "/categories/$ID" request.
+ *
+ * @param rh context of the handler
+ * @param connection the MHD connection to handle
+ * @param[in,out] hc context with further information about the request
+ * @return MHD result code
+ */
+MHD_RESULT
+TMH_private_delete_categories_ID (
+  const struct TMH_RequestHandler *rh,
+  struct MHD_Connection *connection,
+  struct TMH_HandlerContext *hc)
+{
+  struct TMH_MerchantInstance *mi = hc->instance;
+  enum GNUNET_DB_QueryStatus qs;
+  unsigned long long cnum;
+  char dummy;
+
+  (void) rh;
+  GNUNET_assert (NULL != mi);
+  GNUNET_assert (NULL != hc->infix);
+  if (1 != sscanf (hc->infix,
+                   "%llu%c",
+                   &cnum,
+                   &dummy))
+  {
+    GNUNET_break_op (0);
+    return TALER_MHD_reply_with_error (connection,
+                                       MHD_HTTP_BAD_REQUEST,
+                                       TALER_EC_GENERIC_PARAMETER_MALFORMED,
+                                       "category_id must be a number");
+  }
+  qs = TMH_db->delete_category (TMH_db->cls,
+                                mi->settings.id,
+                                cnum);
+  switch (qs)
+  {
+  case GNUNET_DB_STATUS_HARD_ERROR:
+    return TALER_MHD_reply_with_error (connection,
+                                       MHD_HTTP_INTERNAL_SERVER_ERROR,
+                                       TALER_EC_GENERIC_DB_STORE_FAILED,
+                                       "delete_category");
+  case GNUNET_DB_STATUS_SOFT_ERROR:
+    GNUNET_break (0);
+    return TALER_MHD_reply_with_error (connection,
+                                       MHD_HTTP_INTERNAL_SERVER_ERROR,
+                                       TALER_EC_GENERIC_INTERNAL_INVARIANT_FAILURE,
+                                       "delete_category");
+  case GNUNET_DB_STATUS_SUCCESS_NO_RESULTS:
+    return TALER_MHD_reply_with_error (connection,
+                                       MHD_HTTP_NOT_FOUND,
+                                       TALER_EC_MERCHANT_GENERIC_CATEGORY_UNKNOWN,
+                                       hc->infix);
+  case GNUNET_DB_STATUS_SUCCESS_ONE_RESULT:
+    return TALER_MHD_reply_static (connection,
+                                   MHD_HTTP_NO_CONTENT,
+                                   NULL,
+                                   NULL,
+                                   0);
+  }
+  GNUNET_assert (0);
+  return MHD_NO;
+}
+
+
+/* end of taler-merchant-httpd_private-delete-categories-ID.c */
diff --git a/src/backend/taler-merchant-httpd_private-delete-categories-ID.h b/src/backend/taler-merchant-httpd_private-delete-categories-ID.h
new file mode 100644
index 00000000..b17eed49
--- /dev/null
+++ b/src/backend/taler-merchant-httpd_private-delete-categories-ID.h
@@ -0,0 +1,42 @@
+/*
+  This file is part of TALER
+  (C) 2024 Taler Systems SA
+
+  TALER is free software; you can redistribute it and/or modify it under the
+  terms of the GNU Affero General Public License as published by the Free Software
+  Foundation; either version 3, or (at your option) any later version.
+
+  TALER is distributed in the hope that it will be useful, but WITHOUT ANY
+  WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR
+  A PARTICULAR PURPOSE.  See the GNU General Public License for more details.
+
+  You should have received a copy of the GNU General Public License along with
+  TALER; see the file COPYING.  If not, see <http://www.gnu.org/licenses/>
+*/
+/**
+ * @file taler-merchant-httpd_private-delete-categories-ID.h
+ * @brief implement DELETE /private/categories/$ID/
+ * @author Christian Grothoff
+ */
+#ifndef TALER_MERCHANT_HTTPD_PRIVATE_DELETE_CATEGORIES_ID_H
+#define TALER_MERCHANT_HTTPD_PRIVATE_DELETE_CATEGORIES_ID_H
+
+#include "taler-merchant-httpd.h"
+
+
+/**
+ * Handle a DELETE "/categories/$ID" request.
+ *
+ * @param rh context of the handler
+ * @param connection the MHD connection to handle
+ * @param[in,out] hc context with further information about the request
+ * @return MHD result code
+ */
+MHD_RESULT
+TMH_private_delete_categories_ID (
+  const struct TMH_RequestHandler *rh,
+  struct MHD_Connection *connection,
+  struct TMH_HandlerContext *hc);
+
+/* end of taler-merchant-httpd_private-delete-categories-ID.h */
+#endif
diff --git a/src/backend/taler-merchant-httpd_private-delete-otp-devices-ID.c b/src/backend/taler-merchant-httpd_private-delete-otp-devices-ID.c
index b147b84f..ff9ad2ef 100644
--- a/src/backend/taler-merchant-httpd_private-delete-otp-devices-ID.c
+++ b/src/backend/taler-merchant-httpd_private-delete-otp-devices-ID.c
@@ -61,7 +61,7 @@ TMH_private_delete_otp_devices_ID (const struct TMH_RequestHandler *rh,
   case GNUNET_DB_STATUS_SUCCESS_NO_RESULTS:
     return TALER_MHD_reply_with_error (connection,
                                        MHD_HTTP_NOT_FOUND,
-                                       TALER_EC_MERCHANT_GENERIC_TEMPLATE_UNKNOWN,
+                                       TALER_EC_MERCHANT_GENERIC_OTP_DEVICE_UNKNOWN,
                                        hc->infix);
   case GNUNET_DB_STATUS_SUCCESS_ONE_RESULT:
     return TALER_MHD_reply_static (connection,
diff --git a/src/backend/taler-merchant-httpd_private-delete-products-ID.c b/src/backend/taler-merchant-httpd_private-delete-products-ID.c
index 7d314785..23b6de3c 100644
--- a/src/backend/taler-merchant-httpd_private-delete-products-ID.c
+++ b/src/backend/taler-merchant-httpd_private-delete-products-ID.c
@@ -59,22 +59,30 @@ TMH_private_delete_products_ID (const struct TMH_RequestHandler *rh,
                                        TALER_EC_GENERIC_INTERNAL_INVARIANT_FAILURE,
                                        "delete_product (soft)");
   case GNUNET_DB_STATUS_SUCCESS_NO_RESULTS:
-    /* check if deletion must have failed because of locks by
-       checking if the product exists */
-    qs = TMH_db->lookup_product (TMH_db->cls,
-                                 mi->settings.id,
-                                 hc->infix,
-                                 NULL);
-    if (GNUNET_DB_STATUS_HARD_ERROR == qs)
-      return TALER_MHD_reply_with_error (connection,
-                                         MHD_HTTP_INTERNAL_SERVER_ERROR,
-                                         TALER_EC_GENERIC_DB_STORE_FAILED,
-                                         "lookup_product");
-    if (GNUNET_DB_STATUS_SUCCESS_NO_RESULTS == qs)
-      return TALER_MHD_reply_with_error (connection,
-                                         MHD_HTTP_NOT_FOUND,
-                                         TALER_EC_MERCHANT_GENERIC_PRODUCT_UNKNOWN,
-                                         hc->infix);
+    {
+      size_t num_categories = 0;
+      uint64_t *categories = NULL;
+
+      /* check if deletion must have failed because of locks by
+         checking if the product exists */
+      qs = TMH_db->lookup_product (TMH_db->cls,
+                                   mi->settings.id,
+                                   hc->infix,
+                                   NULL,
+                                   &num_categories,
+                                   &categories);
+      if (GNUNET_DB_STATUS_HARD_ERROR == qs)
+        return TALER_MHD_reply_with_error (connection,
+                                           MHD_HTTP_INTERNAL_SERVER_ERROR,
+                                           TALER_EC_GENERIC_DB_STORE_FAILED,
+                                           "lookup_product");
+      if (GNUNET_DB_STATUS_SUCCESS_NO_RESULTS == qs)
+        return TALER_MHD_reply_with_error (connection,
+                                           MHD_HTTP_NOT_FOUND,
+                                           TALER_EC_MERCHANT_GENERIC_PRODUCT_UNKNOWN,
+                                           hc->infix);
+      GNUNET_free (categories);
+    }
     return TALER_MHD_reply_with_error (
       connection,
       MHD_HTTP_CONFLICT,
diff --git a/src/backend/taler-merchant-httpd_private-get-categories-ID.c b/src/backend/taler-merchant-httpd_private-get-categories-ID.c
new file mode 100644
index 00000000..02ef3495
--- /dev/null
+++ b/src/backend/taler-merchant-httpd_private-get-categories-ID.c
@@ -0,0 +1,119 @@
+/*
+  This file is part of TALER
+  (C) 2022-2024 Taler Systems SA
+
+  TALER is free software; you can redistribute it and/or modify it under the
+  terms of the GNU Affero General Public License as published by the Free Software
+  Foundation; either version 3, or (at your option) any later version.
+
+  TALER is distributed in the hope that it will be useful, but WITHOUT ANY
+  WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR
+  A PARTICULAR PURPOSE.  See the GNU General Public License for more details.
+
+  You should have received a copy of the GNU General Public License along with
+  TALER; see the file COPYING.  If not, see <http://www.gnu.org/licenses/>
+*/
+/**
+ * @file taler-merchant-httpd_private-get-categories-ID.c
+ * @brief implement GET /private/categories/$ID
+ * @author Christian Grothoff
+ */
+#include "platform.h"
+#include "taler-merchant-httpd_private-get-categories-ID.h"
+#include <taler/taler_json_lib.h>
+
+
+/**
+ * Handle a GET "/private/categories/$ID" request.
+ *
+ * @param rh context of the handler
+ * @param connection the MHD connection to handle
+ * @param[in,out] hc context with further information about the request
+ * @return MHD result code
+ */
+MHD_RESULT
+TMH_private_get_categories_ID (
+  const struct TMH_RequestHandler *rh,
+  struct MHD_Connection *connection,
+  struct TMH_HandlerContext *hc)
+{
+  struct TMH_MerchantInstance *mi = hc->instance;
+  enum GNUNET_DB_QueryStatus qs;
+  unsigned long long cnum;
+  char dummy;
+  struct TALER_MERCHANTDB_CategoryDetails cd;
+
+  GNUNET_assert (NULL != mi);
+  GNUNET_assert (NULL != hc->infix);
+  if (1 != sscanf (hc->infix,
+                   "%llu%c",
+                   &cnum,
+                   &dummy))
+  {
+    GNUNET_break_op (0);
+    return TALER_MHD_reply_with_error (connection,
+                                       MHD_HTTP_BAD_REQUEST,
+                                       TALER_EC_GENERIC_PARAMETER_MALFORMED,
+                                       "category_id must be a number");
+  }
+
+  qs = TMH_db->select_category (TMH_db->cls,
+                                mi->settings.id,
+                                cnum,
+                                &cd);
+  if (0 > qs)
+  {
+    GNUNET_break (0);
+    return TALER_MHD_reply_with_error (connection,
+                                       MHD_HTTP_INTERNAL_SERVER_ERROR,
+                                       TALER_EC_GENERIC_DB_FETCH_FAILED,
+                                       "select_category");
+  }
+  if (GNUNET_DB_STATUS_SUCCESS_NO_RESULTS == qs)
+  {
+    return TALER_MHD_reply_with_error (connection,
+                                       MHD_HTTP_NOT_FOUND,
+                                       TALER_EC_MERCHANT_GENERIC_CATEGORY_UNKNOWN,
+                                       hc->infix);
+  }
+  {
+    MHD_RESULT ret;
+    json_t *products;
+
+    products = json_array ();
+    GNUNET_assert (NULL != products);
+    for (unsigned int i = 0; i<cd.num_products; i++)
+    {
+      const struct TALER_MERCHANTDB_ProductSummary *product
+        = &cd.products[i];
+      json_t *jprod;
+
+      jprod = GNUNET_JSON_PACK (
+        GNUNET_JSON_pack_string ("product_id",
+                                 product->product_id),
+        GNUNET_JSON_pack_string ("description",
+                                 product->description),
+        GNUNET_JSON_pack_object_steal ("description_i18n",
+                                       product->description_i18n));
+      GNUNET_assert (0 ==
+                     json_array_append_new (products,
+                                            jprod));
+    }
+
+    ret = TALER_MHD_REPLY_JSON_PACK (
+      connection,
+      MHD_HTTP_OK,
+      GNUNET_JSON_pack_string ("name",
+                               cd.category_name),
+      GNUNET_JSON_pack_allow_null (
+        GNUNET_JSON_pack_object_incref ("name_i18n",
+                                        cd.category_name_i18n)),
+      GNUNET_JSON_pack_array_steal ("products",
+                                    products));
+    TALER_MERCHANTDB_category_details_free (&cd);
+    return ret;
+  }
+}
+
+
+/* end of taler-merchant-httpd_private-get-categories-ID.c */
diff --git a/src/backend/taler-merchant-httpd_private-get-categories-ID.h b/src/backend/taler-merchant-httpd_private-get-categories-ID.h
new file mode 100644
index 00000000..c0226659
--- /dev/null
+++ b/src/backend/taler-merchant-httpd_private-get-categories-ID.h
@@ -0,0 +1,42 @@
+/*
+  This file is part of TALER
+  (C) 2024 Taler Systems SA
+
+  TALER is free software; you can redistribute it and/or modify it under the
+  terms of the GNU Affero General Public License as published by the Free Software
+  Foundation; either version 3, or (at your option) any later version.
+
+  TALER is distributed in the hope that it will be useful, but WITHOUT ANY
+  WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR
+  A PARTICULAR PURPOSE.  See the GNU General Public License for more details.
+
+  You should have received a copy of the GNU General Public License along with
+  TALER; see the file COPYING.  If not, see <http://www.gnu.org/licenses/>
+*/
+/**
+ * @file taler-merchant-httpd_private-get-categories-ID.h
+ * @brief implement GET /private/categories/$ID/
+ * @author Christian Grothoff
+ */
+#ifndef TALER_MERCHANT_HTTPD_PRIVATE_GET_CATEGORIES_ID_H
+#define TALER_MERCHANT_HTTPD_PRIVATE_GET_CATEGORIES_ID_H
+
+#include "taler-merchant-httpd.h"
+
+
+/**
+ * Handle a GET "/private/categories/$ID" request.
+ *
+ * @param rh context of the handler
+ * @param connection the MHD connection to handle
+ * @param[in,out] hc context with further information about the request
+ * @return MHD result code
+ */
+MHD_RESULT
+TMH_private_get_categories_ID (
+  const struct TMH_RequestHandler *rh,
+  struct MHD_Connection *connection,
+  struct TMH_HandlerContext *hc);
+
+/* end of taler-merchant-httpd_private-get-categories-ID.h */
+#endif
diff --git a/src/backend/taler-merchant-httpd_private-get-categories.c b/src/backend/taler-merchant-httpd_private-get-categories.c
new file mode 100644
index 00000000..8ebccb2b
--- /dev/null
+++ b/src/backend/taler-merchant-httpd_private-get-categories.c
@@ -0,0 +1,93 @@
+/*
+  This file is part of TALER
+  (C) 2024 Taler Systems SA
+
+  TALER is free software; you can redistribute it and/or modify it under the
+  terms of the GNU Affero General Public License as published by the Free Software
+  Foundation; either version 3, or (at your option) any later version.
+
+  TALER is distributed in the hope that it will be useful, but WITHOUT ANY
+  WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR
+  A PARTICULAR PURPOSE.  See the GNU General Public License for more details.
+
+  You should have received a copy of the GNU General Public License along with
+  TALER; see the file COPYING.  If not, see <http://www.gnu.org/licenses/>
+*/
+/**
+ * @file taler-merchant-httpd_private-get-categories.c
+ * @brief implement GET /categories
+ * @author Christian Grothoff
+ */
+#include "platform.h"
+#include "taler-merchant-httpd_private-get-categories.h"
+
+
+/**
+ * Add category details to our JSON array.
+ *
+ * @param cls a `json_t *` JSON array to build
+ * @param category_id ID of the category
+ * @param category_name name of the category
+ * @param category_name_i18n translations of the @a category_name
+ * @param product_count number of products in the category
+ */
+static void
+add_category (void *cls,
+              uint64_t category_id,
+              const char *category_name,
+              const json_t *category_name_i18n,
+              uint64_t product_count)
+{
+  json_t *pa = cls;
+
+  GNUNET_assert (
+    0 ==
+    json_array_append_new (
+      pa,
+      GNUNET_JSON_PACK (
+        GNUNET_JSON_pack_uint64 (
+          "category_id",
+          category_id),
+        GNUNET_JSON_pack_string (
+          "name",
+          category_name),
+        GNUNET_JSON_pack_object_incref (
+          "name_i18n",
+          (json_t *) category_name_i18n),
+        GNUNET_JSON_pack_uint64 (
+          "product_count",
+          product_count))));
+}
+
+
+MHD_RESULT
+TMH_private_get_categories (const struct TMH_RequestHandler *rh,
+                            struct MHD_Connection *connection,
+                            struct TMH_HandlerContext *hc)
+{
+  json_t *pa;
+  enum GNUNET_DB_QueryStatus qs;
+
+  pa = json_array ();
+  GNUNET_assert (NULL != pa);
+  qs = TMH_db->lookup_categories (TMH_db->cls,
+                                  hc->instance->settings.id,
+                                  &add_category,
+                                  pa);
+  if (0 > qs)
+  {
+    GNUNET_break (0);
+    json_decref (pa);
+    return TALER_MHD_reply_with_error (connection,
+                                       MHD_HTTP_INTERNAL_SERVER_ERROR,
+                                       TALER_EC_GENERIC_DB_FETCH_FAILED,
+                                       NULL);
+  }
+  return TALER_MHD_REPLY_JSON_PACK (connection,
+                                    MHD_HTTP_OK,
+                                    GNUNET_JSON_pack_array_steal ("categories",
+                                                                  pa));
+}
+
+
+/* end of taler-merchant-httpd_private-get-categories.c */
diff --git a/src/backend/taler-merchant-httpd_private-get-categories.h b/src/backend/taler-merchant-httpd_private-get-categories.h
new file mode 100644
index 00000000..68eed05e
--- /dev/null
+++ b/src/backend/taler-merchant-httpd_private-get-categories.h
@@ -0,0 +1,42 @@
+/*
+  This file is part of TALER
+  (C) 2024 Taler Systems SA
+
+  TALER is free software; you can redistribute it and/or modify it under the
+  terms of the GNU Affero General Public License as published by the Free Software
+  Foundation; either version 3, or (at your option) any later version.
+
+  TALER is distributed in the hope that it will be useful, but WITHOUT ANY
+  WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR
+  A PARTICULAR PURPOSE.  See the GNU General Public License for more details.
+
+  You should have received a copy of the GNU General Public License along with
+  TALER; see the file COPYING.  If not, see <http://www.gnu.org/licenses/>
+*/
+/**
+ * @file taler-merchant-httpd_private-get-categories.h
+ * @brief implement GET /private/categories
+ * @author Christian Grothoff
+ */
+#ifndef TALER_MERCHANT_HTTPD_PRIVATE_GET_CATEGORIES_H
+#define TALER_MERCHANT_HTTPD_PRIVATE_GET_CATEGORIES_H
+
+#include "taler-merchant-httpd.h"
+
+
+/**
+ * Handle a GET "/private/categories" request.
+ *
+ * @param rh context of the handler
+ * @param connection the MHD connection to handle
+ * @param[in,out] hc context with further information about the request
+ * @return MHD result code
+ */
+MHD_RESULT
+TMH_private_get_categories (
+  const struct TMH_RequestHandler *rh,
+  struct MHD_Connection *connection,
+  struct TMH_HandlerContext *hc);
+
+/* end of taler-merchant-httpd_private-get-categories.h */
+#endif
diff --git a/src/backend/taler-merchant-httpd_private-get-instances-ID-kyc.c b/src/backend/taler-merchant-httpd_private-get-instances-ID-kyc.c
index 8a338e7d..0382b742 100644
--- a/src/backend/taler-merchant-httpd_private-get-instances-ID-kyc.c
+++ b/src/backend/taler-merchant-httpd_private-get-instances-ID-kyc.c
@@ -684,7 +684,7 @@ kyc_with_exchange (void *cls,
     keys,
     ekr->exchange_kyc_serial,
     &h_payto,
-    ekr->kc->mi->settings.ut,
+    1, /* FIXME: this will go away! */
     GNUNET_TIME_absolute_get_remaining (kc->timeout),
     &exchange_check_cb,
     ekr);
diff --git a/src/backend/taler-merchant-httpd_private-get-instances-ID.c b/src/backend/taler-merchant-httpd_private-get-instances-ID.c
index adc99c39..c8cd2c12 100644
--- a/src/backend/taler-merchant-httpd_private-get-instances-ID.c
+++ b/src/backend/taler-merchant-httpd_private-get-instances-ID.c
@@ -79,7 +79,7 @@ get_instances_ID (struct TMH_MerchantInstance *mi,
                              mi->settings.name),
     GNUNET_JSON_pack_string (
       "user_type",
-      TALER_KYCLOGIC_kyc_user_type2s (mi->settings.ut)),
+      "business"),
     GNUNET_JSON_pack_allow_null (
       GNUNET_JSON_pack_string ("website",
                                mi->settings.website)),
diff --git a/src/backend/taler-merchant-httpd_private-get-instances.c b/src/backend/taler-merchant-httpd_private-get-instances.c
index 50b5c0c2..0220d4df 100644
--- a/src/backend/taler-merchant-httpd_private-get-instances.c
+++ b/src/backend/taler-merchant-httpd_private-get-instances.c
@@ -76,7 +76,7 @@ add_instance (void *cls,
                                               mi->settings.name),
                      GNUNET_JSON_pack_string (
                        "user_type",
-                       TALER_KYCLOGIC_kyc_user_type2s (mi->settings.ut)),
+                       "business"),
                      GNUNET_JSON_pack_allow_null (
                        GNUNET_JSON_pack_string ("website",
                                                 mi->settings.website)),
diff --git a/src/backend/taler-merchant-httpd_private-get-pos.c b/src/backend/taler-merchant-httpd_private-get-pos.c
new file mode 100644
index 00000000..4c14b6ae
--- /dev/null
+++ b/src/backend/taler-merchant-httpd_private-get-pos.c
@@ -0,0 +1,148 @@
+/*
+  This file is part of TALER
+  (C) 2019, 2020, 2021, 2024 Taler Systems SA
+
+  TALER is free software; you can redistribute it and/or modify it under the
+  terms of the GNU Affero General Public License as published by the Free Software
+  Foundation; either version 3, or (at your option) any later version.
+
+  TALER is distributed in the hope that it will be useful, but WITHOUT ANY
+  WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR
+  A PARTICULAR PURPOSE.  See the GNU General Public License for more details.
+
+  You should have received a copy of the GNU General Public License along with
+  TALER; see the file COPYING.  If not, see <http://www.gnu.org/licenses/>
+*/
+/**
+ * @file taler-merchant-httpd_private-get-pos.c
+ * @brief implement GET /private/pos
+ * @author Christian Grothoff
+ */
+#include "platform.h"
+#include "taler-merchant-httpd_private-get-pos.h"
+
+
+/**
+ * Closure for add_product().
+ */
+struct Context
+{
+  /**
+   * JSON array of products we are building.
+   */
+  json_t *pa;
+
+  /**
+   * JSON array of categories we are building.
+   */
+  json_t *ca;
+
+};
+
+
+/**
+ * Add product details to our JSON array.
+ *
+ * @param ctx a `struct Context` with JSON arrays to build
+ * @param product_id ID of the product
+ */
+static void
+add_product (void *cls,
+             uint64_t product_serial,
+             const char *product_id,
+             const struct TALER_MERCHANTDB_ProductDetails *pd,
+             size_t num_categories,
+             const uint64_t *categories)
+{
+  struct Context *ctx = cls;
+  json_t *pa = ctx->pa;
+  json_t *cata;
+
+  cata = json_array ();
+  GNUNET_assert (NULL != cata);
+  for (size_t i = 0; i<num_categories; i++)
+    GNUNET_assert (
+      0 == json_array_append_new (
+        cata,
+        json_integer (categories[i])));
+  GNUNET_assert (
+    0 ==
+    json_array_append_new (
+      pa,
+      GNUNET_JSON_PACK (
+        GNUNET_JSON_pack_string ("description",
+                                 pd->description),
+        GNUNET_JSON_pack_object_incref ("description_i18n",
+                                        (json_t *) pd->description_i18n),
+        GNUNET_JSON_pack_string ("unit",
+                                 pd->unit),
+        TALER_JSON_pack_amount ("price",
+                                &pd->price),
+        GNUNET_JSON_pack_allow_null (
+          GNUNET_JSON_pack_string ("image",
+                                   pd->image)),
+        GNUNET_JSON_pack_array_steal ("categories",
+                                      cata),
+        GNUNET_JSON_pack_allow_null (
+          GNUNET_JSON_pack_array_incref ("taxes",
+                                         (json_t *) pd->taxes)),
+        (INT64_MAX == pd->total_stock)
+        ? GNUNET_JSON_pack_int64 ("total_stock",
+                                  pd->total_stock)
+        : GNUNET_JSON_pack_allow_null (
+          GNUNET_JSON_pack_string ("total_stock",
+                                   NULL)),
+        GNUNET_JSON_pack_uint64 ("minimum_age",
+                                 pd->minimum_age),
+        GNUNET_JSON_pack_uint64 ("product_serial",
+                                 product_serial),
+        GNUNET_JSON_pack_string ("product_id",
+                                 product_id))));
+}
+
+
+MHD_RESULT
+TMH_private_get_pos (const struct TMH_RequestHandler *rh,
+                     struct MHD_Connection *connection,
+                     struct TMH_HandlerContext *hc)
+{
+  struct Context ctx;
+  enum GNUNET_DB_QueryStatus qs;
+
+  ctx.pa = json_array ();
+  GNUNET_assert (NULL != ctx.pa);
+  ctx.ca = json_array ();
+  GNUNET_assert (NULL != ctx.ca);
+  GNUNET_assert (
+    0 == json_array_append_new (
+      ctx.ca,
+      GNUNET_JSON_PACK (
+        GNUNET_JSON_pack_uint64 ("id",
+                                 0),
+        GNUNET_JSON_pack_string ("name",
+                                 "default"))));
+  qs = TMH_db->lookup_all_products (TMH_db->cls,
+                                    hc->instance->settings.id,
+                                    &add_product,
+                                    &ctx);
+  if (0 > qs)
+  {
+    GNUNET_break (0);
+    json_decref (ctx.pa);
+    json_decref (ctx.ca);
+    return TALER_MHD_reply_with_error (connection,
+                                       MHD_HTTP_INTERNAL_SERVER_ERROR,
+                                       TALER_EC_GENERIC_DB_FETCH_FAILED,
+                                       NULL);
+  }
+  return TALER_MHD_REPLY_JSON_PACK (
+    connection,
+    MHD_HTTP_OK,
+    GNUNET_JSON_pack_array_steal ("categories",
+                                  ctx.ca),
+    GNUNET_JSON_pack_array_steal ("products",
+                                  ctx.pa));
+}
+
+
+/* end of taler-merchant-httpd_private-get-pos.c */
diff --git a/src/backend/taler-merchant-httpd_private-get-pos.h b/src/backend/taler-merchant-httpd_private-get-pos.h
new file mode 100644
index 00000000..ce266823
--- /dev/null
+++ b/src/backend/taler-merchant-httpd_private-get-pos.h
@@ -0,0 +1,41 @@
+/*
+  This file is part of TALER
+  (C) 2024 Taler Systems SA
+
+  TALER is free software; you can redistribute it and/or modify it under the
+  terms of the GNU Affero General Public License as published by the Free Software
+  Foundation; either version 3, or (at your option) any later version.
+
+  TALER is distributed in the hope that it will be useful, but WITHOUT ANY
+  WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR
+  A PARTICULAR PURPOSE.  See the GNU General Public License for more details.
+
+  You should have received a copy of the GNU General Public License along with
+  TALER; see the file COPYING.  If not, see <http://www.gnu.org/licenses/>
+*/
+/**
+ * @file taler-merchant-httpd_private-get-pos.h
+ * @brief implement GET /pos
+ * @author Christian Grothoff
+ */
+#ifndef TALER_MERCHANT_HTTPD_PRIVATE_GET_POS_H
+#define TALER_MERCHANT_HTTPD_PRIVATE_GET_POS_H
+
+#include "taler-merchant-httpd.h"
+
+
+/**
+ * Handle a GET "/pos" request.
+ *
+ * @param rh context of the handler
+ * @param connection the MHD connection to handle
+ * @param[in,out] hc context with further information about the request
+ * @return MHD result code
+ */
+MHD_RESULT
+TMH_private_get_pos (const struct TMH_RequestHandler *rh,
+                     struct MHD_Connection *connection,
+                     struct TMH_HandlerContext *hc);
+
+/* end of taler-merchant-httpd_private-get-pos.h */
+#endif
diff --git a/src/backend/taler-merchant-httpd_private-get-products-ID.c b/src/backend/taler-merchant-httpd_private-get-products-ID.c
index 1406349f..0729b1df 100644
--- a/src/backend/taler-merchant-httpd_private-get-products-ID.c
+++ b/src/backend/taler-merchant-httpd_private-get-products-ID.c
@@ -32,19 +32,25 @@
  * @return MHD result code
  */
 MHD_RESULT
-TMH_private_get_products_ID (const struct TMH_RequestHandler *rh,
-                             struct MHD_Connection *connection,
-                             struct TMH_HandlerContext *hc)
+TMH_private_get_products_ID (
+  const struct TMH_RequestHandler *rh,
+  struct MHD_Connection *connection,
+  struct TMH_HandlerContext *hc)
 {
   struct TMH_MerchantInstance *mi = hc->instance;
   struct TALER_MERCHANTDB_ProductDetails pd = { 0 };
   enum GNUNET_DB_QueryStatus qs;
+  size_t num_categories = 0;
+  uint64_t *categories = NULL;
+  json_t *jcategories;
 
   GNUNET_assert (NULL != mi);
   qs = TMH_db->lookup_product (TMH_db->cls,
                                mi->settings.id,
                                hc->infix,
-                               &pd);
+                               &pd,
+                               &num_categories,
+                               &categories);
   if (0 > qs)
   {
     GNUNET_break (0);
@@ -60,6 +66,16 @@ TMH_private_get_products_ID (const struct TMH_RequestHandler *rh,
                                        TALER_EC_MERCHANT_GENERIC_PRODUCT_UNKNOWN,
                                        hc->infix);
   }
+  jcategories = json_array ();
+  GNUNET_assert (NULL != jcategories);
+  for (size_t i = 0; i<num_categories; i++)
+  {
+    GNUNET_assert (0 ==
+                   json_array_append_new (jcategories,
+                                          json_integer (categories[i])));
+  }
+  GNUNET_free (categories);
+
   {
     MHD_RESULT ret;
 
@@ -72,12 +88,16 @@ TMH_private_get_products_ID (const struct TMH_RequestHandler *rh,
                                      pd.description_i18n),
       GNUNET_JSON_pack_string ("unit",
                                pd.unit),
+      GNUNET_JSON_pack_array_steal ("categories",
+                                    jcategories),
       TALER_JSON_pack_amount ("price",
                               &pd.price),
-      GNUNET_JSON_pack_string ("image",
-                               pd.image),
-      GNUNET_JSON_pack_array_steal ("taxes",
-                                    pd.taxes),
+      GNUNET_JSON_pack_allow_null (
+        GNUNET_JSON_pack_string ("image",
+                                 pd.image)),
+      GNUNET_JSON_pack_allow_null (
+        GNUNET_JSON_pack_array_steal ("taxes",
+                                      pd.taxes)),
       GNUNET_JSON_pack_int64 ("total_stock",
                               (INT64_MAX == pd.total_stock)
                               ? -1LL
@@ -86,8 +106,9 @@ TMH_private_get_products_ID (const struct TMH_RequestHandler *rh,
                                pd.total_sold),
       GNUNET_JSON_pack_uint64 ("total_lost",
                                pd.total_lost),
-      GNUNET_JSON_pack_object_steal ("address",
-                                     pd.address),
+      GNUNET_JSON_pack_allow_null (
+        GNUNET_JSON_pack_object_steal ("address",
+                                       pd.address)),
       GNUNET_JSON_pack_allow_null (
         GNUNET_JSON_pack_timestamp ("next_restock",
                                     (pd.next_restock))),
diff --git a/src/backend/taler-merchant-httpd_private-patch-categories-ID.c b/src/backend/taler-merchant-httpd_private-patch-categories-ID.c
new file mode 100644
index 00000000..1aa489cf
--- /dev/null
+++ b/src/backend/taler-merchant-httpd_private-patch-categories-ID.c
@@ -0,0 +1,120 @@
+/*
+  This file is part of TALER
+  (C) 2024 Taler Systems SA
+
+  TALER is free software; you can redistribute it and/or modify
+  it under the terms of the GNU Affero General Public License as
+  published by the Free Software Foundation; either version 3,
+  or (at your option) any later version.
+
+  TALER is distributed in the hope that it will be useful, but
+  WITHOUT ANY WARRANTY; without even the implied warranty of
+  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+  GNU General Public License for more details.
+
+  You should have received a copy of the GNU General Public
+  License along with TALER; see the file COPYING.  If not,
+  see <http://www.gnu.org/licenses/>
+*/
+
+/**
+ * @file taler-merchant-httpd_private-patch-categories-ID.c
+ * @brief implementing PATCH /categories/$ID request handling
+ * @author Christian Grothoff
+ */
+#include "platform.h"
+#include "taler-merchant-httpd_private-patch-categories-ID.h"
+#include "taler-merchant-httpd_helper.h"
+#include <taler/taler_json_lib.h>
+
+
+MHD_RESULT
+TMH_private_patch_categories_ID (const struct TMH_RequestHandler *rh,
+                                 struct MHD_Connection *connection,
+                                 struct TMH_HandlerContext *hc)
+{
+  struct TMH_MerchantInstance *mi = hc->instance;
+  unsigned long long cnum;
+  char dummy;
+  const char *category_name;
+  const json_t *category_name_i18n;
+  struct GNUNET_JSON_Specification spec[] = {
+    GNUNET_JSON_spec_string ("name",
+                             &category_name),
+    GNUNET_JSON_spec_object_const ("name_i18n",
+                                   &category_name_i18n),
+    GNUNET_JSON_spec_end ()
+  };
+  enum GNUNET_DB_QueryStatus qs;
+
+  GNUNET_assert (NULL != mi);
+  GNUNET_assert (NULL != hc->infix);
+  if (1 != sscanf (hc->infix,
+                   "%llu%c",
+                   &cnum,
+                   &dummy))
+  {
+    GNUNET_break_op (0);
+    return TALER_MHD_reply_with_error (connection,
+                                       MHD_HTTP_BAD_REQUEST,
+                                       TALER_EC_GENERIC_PARAMETER_MALFORMED,
+                                       "category_id must be a number");
+  }
+
+  {
+    enum GNUNET_GenericReturnValue res;
+
+    res = TALER_MHD_parse_json_data (connection,
+                                     hc->request_body,
+                                     spec);
+    if (GNUNET_OK != res)
+      return (GNUNET_NO == res)
+             ? MHD_YES
+             : MHD_NO;
+  }
+
+  qs = TMH_db->update_category (TMH_db->cls,
+                                mi->settings.id,
+                                cnum,
+                                category_name,
+                                category_name_i18n);
+  {
+    MHD_RESULT ret = MHD_NO;
+
+    switch (qs)
+    {
+    case GNUNET_DB_STATUS_HARD_ERROR:
+      GNUNET_break (0);
+      ret = TALER_MHD_reply_with_error (connection,
+                                        MHD_HTTP_INTERNAL_SERVER_ERROR,
+                                        TALER_EC_GENERIC_DB_STORE_FAILED,
+                                        "update_category");
+      break;
+    case GNUNET_DB_STATUS_SOFT_ERROR:
+      GNUNET_break (0);
+      ret = TALER_MHD_reply_with_error (connection,
+                                        MHD_HTTP_INTERNAL_SERVER_ERROR,
+                                        TALER_EC_GENERIC_INTERNAL_INVARIANT_FAILURE,
+                                        "unexpected serialization problem");
+      break;
+    case GNUNET_DB_STATUS_SUCCESS_NO_RESULTS:
+      ret = TALER_MHD_reply_with_error (connection,
+                                        MHD_HTTP_NOT_FOUND,
+                                        TALER_EC_MERCHANT_GENERIC_CATEGORY_UNKNOWN,
+                                        category_name);
+      break;
+    case GNUNET_DB_STATUS_SUCCESS_ONE_RESULT:
+      ret = TALER_MHD_reply_static (connection,
+                                    MHD_HTTP_NO_CONTENT,
+                                    NULL,
+                                    NULL,
+                                    0);
+      break;
+    }
+    GNUNET_JSON_parse_free (spec);
+    return ret;
+  }
+}
+
+
+/* end of taler-merchant-httpd_private-patch-categories-ID.c */
diff --git a/src/backend/taler-merchant-httpd_private-patch-categories-ID.h b/src/backend/taler-merchant-httpd_private-patch-categories-ID.h
new file mode 100644
index 00000000..c88290a8
--- /dev/null
+++ b/src/backend/taler-merchant-httpd_private-patch-categories-ID.h
@@ -0,0 +1,45 @@
+/*
+  This file is part of TALER
+  (C) 2024 Taler Systems SA
+
+  TALER is free software; you can redistribute it and/or modify
+  it under the terms of the GNU Affero General Public License as
+  published by the Free Software Foundation; either version 3,
+  or (at your option) any later version.
+
+  TALER is distributed in the hope that it will be useful, but
+  WITHOUT ANY WARRANTY; without even the implied warranty of
+  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+  GNU General Public License for more details.
+
+  You should have received a copy of the GNU General Public
+  License along with TALER; see the file COPYING.  If not,
+  see <http://www.gnu.org/licenses/>
+*/
+
+/**
+ * @file taler-merchant-httpd_private-patch-categories-ID.h
+ * @brief implementing PATCH /private/categories/$ID request handling
+ * @author Christian Grothoff
+ */
+#ifndef TALER_MERCHANT_HTTPD_PRIVATE_PATCH_CATEGORIES_ID_H
+#define TALER_MERCHANT_HTTPD_PRIVATE_PATCH_CATEGORIES_ID_H
+
+#include "taler-merchant-httpd.h"
+
+
+/**
+ * PATCH descriptions of an existing product category.
+ *
+ * @param rh context of the handler
+ * @param connection the MHD connection to handle
+ * @param[in,out] hc context with further information about the request
+ * @return MHD result code
+ */
+MHD_RESULT
+TMH_private_patch_categories_ID (
+  const struct TMH_RequestHandler *rh,
+  struct MHD_Connection *connection,
+  struct TMH_HandlerContext *hc);
+
+#endif
diff --git a/src/backend/taler-merchant-httpd_private-patch-instances-ID.c b/src/backend/taler-merchant-httpd_private-patch-instances-ID.c
index 027d5869..70df009e 100644
--- a/src/backend/taler-merchant-httpd_private-patch-instances-ID.c
+++ b/src/backend/taler-merchant-httpd_private-patch-instances-ID.c
@@ -64,17 +64,12 @@ patch_instances_ID (struct TMH_MerchantInstance *mi,
 {
   struct TALER_MERCHANTDB_InstanceSettings is;
   const char *name;
-  const char *uts = "business";
   struct TMH_WireMethod *wm_head = NULL;
   struct TMH_WireMethod *wm_tail = NULL;
   struct GNUNET_JSON_Specification spec[] = {
     GNUNET_JSON_spec_string ("name",
                              &name),
     GNUNET_JSON_spec_mark_optional (
-      GNUNET_JSON_spec_string ("user_type",
-                               &uts),
-      NULL),
-    GNUNET_JSON_spec_mark_optional (
       GNUNET_JSON_spec_string ("website",
                                (const char **) &is.website),
       NULL),
@@ -115,19 +110,6 @@ patch_instances_ID (struct TMH_MerchantInstance *mi,
              ? MHD_YES
              : MHD_NO;
   }
-  if (NULL == uts)
-    uts = "business";
-  if (GNUNET_OK !=
-      TALER_KYCLOGIC_kyc_user_type_from_string (uts,
-                                                &is.ut))
-  {
-    GNUNET_break_op (0);
-    GNUNET_JSON_parse_free (spec);
-    return TALER_MHD_reply_with_error (connection,
-                                       MHD_HTTP_BAD_REQUEST,
-                                       TALER_EC_GENERIC_PARAMETER_MALFORMED,
-                                       "user_type");
-  }
   if (! TMH_location_object_valid (is.address))
   {
     GNUNET_break_op (0);
@@ -185,7 +167,6 @@ patch_instances_ID (struct TMH_MerchantInstance *mi,
     /* Check for equality of settings */
     if (! ( (0 == strcmp (mi->settings.name,
                           name)) &&
-            (mi->settings.ut == is.ut) &&
             ((mi->settings.email == is.email) ||
              (NULL != is.email && NULL != mi->settings.email &&
               0 == strcmp (mi->settings.email,
@@ -240,7 +221,6 @@ giveup:
   json_decref (mi->settings.jurisdiction);
   is.id = mi->settings.id;
   mi->settings = is;
-  // mi->settings.user_type = (enum TALER_KYCLOGIC_KycUserType) is.user_type;
   mi->settings.address = json_incref (mi->settings.address);
   mi->settings.jurisdiction = json_incref (mi->settings.jurisdiction);
   mi->settings.name = GNUNET_strdup (name);
diff --git a/src/backend/taler-merchant-httpd_private-patch-products-ID.c b/src/backend/taler-merchant-httpd_private-patch-products-ID.c
index 7bc327cd..6e50cced 100644
--- a/src/backend/taler-merchant-httpd_private-patch-products-ID.c
+++ b/src/backend/taler-merchant-httpd_private-patch-products-ID.c
@@ -1,6 +1,6 @@
 /*
   This file is part of TALER
-  (C) 2020 Taler Systems SA
+  (C) 2020-2024 Taler Systems SA
 
   TALER is free software; you can redistribute it and/or modify
   it under the terms of the GNU Affero General Public License as
@@ -29,76 +29,6 @@
 
 
 /**
- * How often do we retry the simple INSERT database transaction?
- */
-#define MAX_RETRIES 3
-
-
-/**
- * Determine the cause of the PATCH failure in more detail and report.
- *
- * @param connection connection to report on
- * @param instance_id instance we are processing
- * @param product_id ID of the product to patch
- * @param pd product details we failed to set
- */
-static MHD_RESULT
-determine_cause (struct MHD_Connection *connection,
-                 const char *instance_id,
-                 const char *product_id,
-                 const struct TALER_MERCHANTDB_ProductDetails *pd)
-{
-  struct TALER_MERCHANTDB_ProductDetails pdx;
-  enum GNUNET_DB_QueryStatus qs;
-
-  qs = TMH_db->lookup_product (TMH_db->cls,
-                               instance_id,
-                               product_id,
-                               &pdx);
-  switch (qs)
-  {
-  case GNUNET_DB_STATUS_HARD_ERROR:
-    GNUNET_break (0);
-    return TALER_MHD_reply_with_error (connection,
-                                       MHD_HTTP_INTERNAL_SERVER_ERROR,
-                                       TALER_EC_GENERIC_DB_FETCH_FAILED,
-                                       NULL);
-  case GNUNET_DB_STATUS_SOFT_ERROR:
-    GNUNET_break (0);
-    return TALER_MHD_reply_with_error (connection,
-                                       MHD_HTTP_INTERNAL_SERVER_ERROR,
-                                       TALER_EC_GENERIC_INTERNAL_INVARIANT_FAILURE,
-                                       "unexpected serialization problem");
-  case GNUNET_DB_STATUS_SUCCESS_NO_RESULTS:
-    return TALER_MHD_reply_with_error (connection,
-                                       MHD_HTTP_NOT_FOUND,
-                                       TALER_EC_MERCHANT_GENERIC_PRODUCT_UNKNOWN,
-                                       product_id);
-  case GNUNET_DB_STATUS_SUCCESS_ONE_RESULT:
-    break; /* do below */
-  }
-
-  {
-    enum TALER_ErrorCode ec;
-
-    ec = TALER_EC_GENERIC_INTERNAL_INVARIANT_FAILURE;
-    if (pdx.total_lost > pd->total_lost)
-      ec = TALER_EC_MERCHANT_PRIVATE_PATCH_PRODUCTS_TOTAL_LOST_REDUCED;
-    if (pdx.total_sold > pd->total_sold)
-      ec = TALER_EC_MERCHANT_PRIVATE_PATCH_PRODUCTS_TOTAL_SOLD_REDUCED;
-    if (pdx.total_stock > pd->total_stock)
-      ec = TALER_EC_MERCHANT_PRIVATE_PATCH_PRODUCTS_TOTAL_STOCKED_REDUCED;
-    TALER_MERCHANTDB_product_details_free (&pdx);
-    GNUNET_break (TALER_EC_GENERIC_INTERNAL_INVARIANT_FAILURE != ec);
-    return TALER_MHD_reply_with_error (connection,
-                                       MHD_HTTP_CONFLICT,
-                                       ec,
-                                       NULL);
-  }
-}
-
-
-/**
  * PATCH configuration of an existing instance, given its configuration.
  *
  * @param rh context of the handler
@@ -107,13 +37,15 @@ determine_cause (struct MHD_Connection *connection,
  * @return MHD result code
  */
 MHD_RESULT
-TMH_private_patch_products_ID (const struct TMH_RequestHandler *rh,
-                               struct MHD_Connection *connection,
-                               struct TMH_HandlerContext *hc)
+TMH_private_patch_products_ID (
+  const struct TMH_RequestHandler *rh,
+  struct MHD_Connection *connection,
+  struct TMH_HandlerContext *hc)
 {
   struct TMH_MerchantInstance *mi = hc->instance;
   const char *product_id = hc->infix;
   struct TALER_MERCHANTDB_ProductDetails pd = {0};
+  const json_t *categories = NULL;
   int64_t total_stock;
   enum GNUNET_DB_QueryStatus qs;
   struct GNUNET_JSON_Specification spec[] = {
@@ -135,6 +67,10 @@ TMH_private_patch_products_ID (const struct TMH_RequestHandler *rh,
       GNUNET_JSON_spec_json ("taxes",
                              &pd.taxes),
       NULL),
+    GNUNET_JSON_spec_mark_optional (
+      GNUNET_JSON_spec_array_const ("categories",
+                                    &categories),
+      NULL),
     GNUNET_JSON_spec_int64 ("total_stock",
                             &total_stock),
     GNUNET_JSON_spec_mark_optional (
@@ -155,6 +91,15 @@ TMH_private_patch_products_ID (const struct TMH_RequestHandler *rh,
       NULL),
     GNUNET_JSON_spec_end ()
   };
+  MHD_RESULT ret;
+  size_t num_cats = 0;
+  uint64_t *cats = NULL;
+  bool no_instance;
+  ssize_t no_cat;
+  bool no_product;
+  bool lost_reduced;
+  bool sold_reduced;
+  bool stock_reduced;
 
   pd.total_sold = 0; /* will be ignored anyway */
   GNUNET_assert (NULL != mi);
@@ -173,11 +118,11 @@ TMH_private_patch_products_ID (const struct TMH_RequestHandler *rh,
   if (total_stock < -1)
   {
     GNUNET_break_op (0);
-    GNUNET_JSON_parse_free (spec);
-    return TALER_MHD_reply_with_error (connection,
-                                       MHD_HTTP_BAD_REQUEST,
-                                       TALER_EC_GENERIC_PARAMETER_MALFORMED,
-                                       "total_stock");
+    ret = TALER_MHD_reply_with_error (connection,
+                                      MHD_HTTP_BAD_REQUEST,
+                                      TALER_EC_GENERIC_PARAMETER_MALFORMED,
+                                      "total_stock");
+    goto cleanup;
   }
   if (-1 == total_stock)
     pd.total_stock = INT64_MAX;
@@ -189,23 +134,45 @@ TMH_private_patch_products_ID (const struct TMH_RequestHandler *rh,
   if (! TMH_location_object_valid (pd.address))
   {
     GNUNET_break_op (0);
-    GNUNET_JSON_parse_free (spec);
-    return TALER_MHD_reply_with_error (connection,
-                                       MHD_HTTP_BAD_REQUEST,
-                                       TALER_EC_GENERIC_PARAMETER_MALFORMED,
-                                       "address");
+    ret = TALER_MHD_reply_with_error (connection,
+                                      MHD_HTTP_BAD_REQUEST,
+                                      TALER_EC_GENERIC_PARAMETER_MALFORMED,
+                                      "address");
+    goto cleanup;
+  }
+  num_cats = json_array_size (categories);
+  cats = GNUNET_new_array (num_cats,
+                           uint64_t);
+  {
+    size_t idx;
+    json_t *val;
+
+    json_array_foreach (categories, idx, val)
+    {
+      if (! json_is_integer (val))
+      {
+        GNUNET_break_op (0);
+        ret = TALER_MHD_reply_with_error (connection,
+                                          MHD_HTTP_BAD_REQUEST,
+                                          TALER_EC_GENERIC_PARAMETER_MALFORMED,
+                                          "categories");
+        goto cleanup;
+      }
+      cats[idx] = json_integer_value (val);
+    }
   }
+
   if (NULL == pd.description_i18n)
     pd.description_i18n = json_object ();
 
   if (! TALER_JSON_check_i18n (pd.description_i18n))
   {
     GNUNET_break_op (0);
-    GNUNET_JSON_parse_free (spec);
-    return TALER_MHD_reply_with_error (connection,
-                                       MHD_HTTP_BAD_REQUEST,
-                                       TALER_EC_GENERIC_PARAMETER_MALFORMED,
-                                       "description_i18n");
+    ret = TALER_MHD_reply_with_error (connection,
+                                      MHD_HTTP_BAD_REQUEST,
+                                      TALER_EC_GENERIC_PARAMETER_MALFORMED,
+                                      "description_i18n");
+    goto cleanup;
   }
 
   if (NULL == pd.taxes)
@@ -214,74 +181,143 @@ TMH_private_patch_products_ID (const struct TMH_RequestHandler *rh,
   if (! TMH_taxes_array_valid (pd.taxes))
   {
     GNUNET_break_op (0);
-    GNUNET_JSON_parse_free (spec);
-    return TALER_MHD_reply_with_error (connection,
-                                       MHD_HTTP_BAD_REQUEST,
-                                       TALER_EC_GENERIC_PARAMETER_MALFORMED,
-                                       "taxes");
+    ret = TALER_MHD_reply_with_error (connection,
+                                      MHD_HTTP_BAD_REQUEST,
+                                      TALER_EC_GENERIC_PARAMETER_MALFORMED,
+                                      "taxes");
+    goto cleanup;
   }
+
   if (NULL == pd.image)
     pd.image = "";
   if (! TMH_image_data_url_valid (pd.image))
   {
     GNUNET_break_op (0);
-    GNUNET_JSON_parse_free (spec);
-    return TALER_MHD_reply_with_error (connection,
-                                       MHD_HTTP_BAD_REQUEST,
-                                       TALER_EC_GENERIC_PARAMETER_MALFORMED,
-                                       "image");
+    ret = TALER_MHD_reply_with_error (connection,
+                                      MHD_HTTP_BAD_REQUEST,
+                                      TALER_EC_GENERIC_PARAMETER_MALFORMED,
+                                      "image");
+    goto cleanup;
   }
+
   if ( (pd.total_stock < pd.total_sold + pd.total_lost) ||
        (pd.total_sold + pd.total_lost < pd.total_sold) /* integer overflow */)
   {
     GNUNET_break_op (0);
-    GNUNET_JSON_parse_free (spec);
-    return TALER_MHD_reply_with_error (
+    ret = TALER_MHD_reply_with_error (
       connection,
       MHD_HTTP_BAD_REQUEST,
       TALER_EC_MERCHANT_PRIVATE_PATCH_PRODUCTS_TOTAL_LOST_EXCEEDS_STOCKS,
       NULL);
+    goto cleanup;
   }
+
   qs = TMH_db->update_product (TMH_db->cls,
                                mi->settings.id,
                                product_id,
-                               &pd);
+                               &pd,
+                               num_cats,
+                               cats,
+                               &no_instance,
+                               &no_cat,
+                               &no_product,
+                               &lost_reduced,
+                               &sold_reduced,
+                               &stock_reduced);
+  switch (qs)
   {
-    MHD_RESULT ret = MHD_NO;
+  case GNUNET_DB_STATUS_HARD_ERROR:
+    GNUNET_break (0);
+    ret = TALER_MHD_reply_with_error (connection,
+                                      MHD_HTTP_INTERNAL_SERVER_ERROR,
+                                      TALER_EC_GENERIC_DB_STORE_FAILED,
+                                      NULL);
+    goto cleanup;
+  case GNUNET_DB_STATUS_SOFT_ERROR:
+    GNUNET_break (0);
+    ret = TALER_MHD_reply_with_error (connection,
+                                      MHD_HTTP_INTERNAL_SERVER_ERROR,
+                                      TALER_EC_GENERIC_INTERNAL_INVARIANT_FAILURE,
+                                      "unexpected serialization problem");
+    goto cleanup;
+  case GNUNET_DB_STATUS_SUCCESS_NO_RESULTS:
+    GNUNET_break (0);
+    ret = TALER_MHD_reply_with_error (connection,
+                                      MHD_HTTP_INTERNAL_SERVER_ERROR,
+                                      TALER_EC_GENERIC_INTERNAL_INVARIANT_FAILURE,
+                                      "unexpected problem in stored procedure");
+    goto cleanup;
+  case GNUNET_DB_STATUS_SUCCESS_ONE_RESULT:
+    break;
+  }
 
-    switch (qs)
-    {
-    case GNUNET_DB_STATUS_HARD_ERROR:
-      GNUNET_break (0);
-      ret = TALER_MHD_reply_with_error (connection,
-                                        MHD_HTTP_INTERNAL_SERVER_ERROR,
-                                        TALER_EC_GENERIC_DB_STORE_FAILED,
-                                        NULL);
-      break;
-    case GNUNET_DB_STATUS_SOFT_ERROR:
-      GNUNET_break (0);
-      ret = TALER_MHD_reply_with_error (connection,
-                                        MHD_HTTP_INTERNAL_SERVER_ERROR,
-                                        TALER_EC_GENERIC_INTERNAL_INVARIANT_FAILURE,
-                                        "unexpected serialization problem");
-      break;
-    case GNUNET_DB_STATUS_SUCCESS_NO_RESULTS:
-      ret = determine_cause (connection,
-                             mi->settings.id,
-                             product_id,
-                             &pd);
-      break;
-    case GNUNET_DB_STATUS_SUCCESS_ONE_RESULT:
-      ret = TALER_MHD_reply_static (connection,
-                                    MHD_HTTP_NO_CONTENT,
-                                    NULL,
-                                    NULL,
-                                    0);
-      break;
-    }
-    GNUNET_JSON_parse_free (spec);
-    return ret;
+  if (no_instance)
+  {
+    ret = TALER_MHD_reply_with_error (connection,
+                                      MHD_HTTP_NOT_FOUND,
+                                      TALER_EC_MERCHANT_GENERIC_INSTANCE_UNKNOWN,
+                                      mi->settings.id);
+    goto cleanup;
+  }
+  if (-1 != no_cat)
+  {
+    char cats[24];
+
+    GNUNET_snprintf (cats,
+                     sizeof (cats),
+                     "%llu",
+                     (unsigned long long) no_cat);
+    ret = TALER_MHD_reply_with_error (connection,
+                                      MHD_HTTP_NOT_FOUND,
+                                      TALER_EC_MERCHANT_GENERIC_CATEGORY_UNKNOWN,
+                                      cats);
+    goto cleanup;
+  }
+  if (no_product)
+  {
+    ret = TALER_MHD_reply_with_error (connection,
+                                      MHD_HTTP_NOT_FOUND,
+                                      TALER_EC_MERCHANT_GENERIC_PRODUCT_UNKNOWN,
+                                      product_id);
+    goto cleanup;
+  }
+  if (lost_reduced)
+  {
+    ret = TALER_MHD_reply_with_error (
+      connection,
+      MHD_HTTP_CONFLICT,
+      TALER_EC_MERCHANT_PRIVATE_PATCH_PRODUCTS_TOTAL_LOST_REDUCED,
+      NULL);
+    goto cleanup;
+  }
+  if (sold_reduced)
+  {
+    ret = TALER_MHD_reply_with_error (
+      connection,
+      MHD_HTTP_CONFLICT,
+      TALER_EC_MERCHANT_PRIVATE_PATCH_PRODUCTS_TOTAL_SOLD_REDUCED,
+      NULL);
+    goto cleanup;
+  }
+  if (stock_reduced)
+  {
+    ret = TALER_MHD_reply_with_error (
+      connection,
+      MHD_HTTP_CONFLICT,
+      TALER_EC_MERCHANT_PRIVATE_PATCH_PRODUCTS_TOTAL_STOCKED_REDUCED,
+      NULL);
+    goto cleanup;
   }
+  /* success! */
+  ret = TALER_MHD_reply_static (connection,
+                                MHD_HTTP_NO_CONTENT,
+                                NULL,
+                                NULL,
+                                0);
+cleanup:
+  GNUNET_free (cats);
+  GNUNET_JSON_parse_free (spec);
+  return ret;
 }
 
 
diff --git a/src/backend/taler-merchant-httpd_private-post-categories.c b/src/backend/taler-merchant-httpd_private-post-categories.c
new file mode 100644
index 00000000..675de765
--- /dev/null
+++ b/src/backend/taler-merchant-httpd_private-post-categories.c
@@ -0,0 +1,170 @@
+/*
+  This file is part of TALER
+  (C) 2024 Taler Systems SA
+
+  TALER is free software; you can redistribute it and/or modify
+  it under the terms of the GNU Affero General Public License as
+  published by the Free Software Foundation; either version 3,
+  or (at your option) any later version.
+
+  TALER is distributed in the hope that it will be useful, but
+  WITHOUT ANY WARRANTY; without even the implied warranty of
+  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+  GNU General Public License for more details.
+
+  You should have received a copy of the GNU General Public
+  License along with TALER; see the file COPYING.  If not,
+  see <http://www.gnu.org/licenses/>
+*/
+/**
+ * @file taler-merchant-httpd_private-post-categories.c
+ * @brief implementing POST /private/categories request handling
+ * @author Christian Grothoff
+ */
+#include "platform.h"
+#include "taler-merchant-httpd_private-post-categories.h"
+#include "taler-merchant-httpd_helper.h"
+#include <taler/taler_json_lib.h>
+
+
+/**
+ * How often do we retry the simple INSERT database transaction?
+ */
+#define MAX_RETRIES 3
+
+
+MHD_RESULT
+TMH_private_post_categories (const struct TMH_RequestHandler *rh,
+                             struct MHD_Connection *connection,
+                             struct TMH_HandlerContext *hc)
+{
+  struct TMH_MerchantInstance *mi = hc->instance;
+  const char *category_name;
+  const json_t *category_name_i18n;
+  uint64_t category_id;
+  struct GNUNET_JSON_Specification spec[] = {
+    GNUNET_JSON_spec_string ("name",
+                             &category_name),
+    GNUNET_JSON_spec_object_const ("name_i18n",
+                                   &category_name_i18n),
+    GNUNET_JSON_spec_end ()
+  };
+  enum GNUNET_DB_QueryStatus qs;
+
+  GNUNET_assert (NULL != mi);
+  {
+    enum GNUNET_GenericReturnValue res;
+
+    res = TALER_MHD_parse_json_data (connection,
+                                     hc->request_body,
+                                     spec);
+    if (GNUNET_OK != res)
+    {
+      GNUNET_break_op (0);
+      return (GNUNET_NO == res)
+             ? MHD_YES
+             : MHD_NO;
+    }
+  }
+
+  /* finally, interact with DB until no serialization error */
+  for (unsigned int i = 0; i<MAX_RETRIES; i++)
+  {
+    json_t *xcategory_name_i18n;
+
+    if (GNUNET_OK !=
+        TMH_db->start (TMH_db->cls,
+                       "POST /categories"))
+    {
+      GNUNET_break (0);
+      GNUNET_JSON_parse_free (spec);
+      return TALER_MHD_reply_with_error (connection,
+                                         MHD_HTTP_INTERNAL_SERVER_ERROR,
+                                         TALER_EC_GENERIC_DB_START_FAILED,
+                                         NULL);
+    }
+    qs = TMH_db->select_category_by_name (TMH_db->cls,
+                                          mi->settings.id,
+                                          category_name,
+                                          &xcategory_name_i18n,
+                                          &category_id);
+    switch (qs)
+    {
+    case GNUNET_DB_STATUS_HARD_ERROR:
+      /* Clean up and fail hard */
+      GNUNET_break (0);
+      TMH_db->rollback (TMH_db->cls);
+      GNUNET_JSON_parse_free (spec);
+      return TALER_MHD_reply_with_error (connection,
+                                         MHD_HTTP_INTERNAL_SERVER_ERROR,
+                                         TALER_EC_GENERIC_DB_FETCH_FAILED,
+                                         NULL);
+    case GNUNET_DB_STATUS_SOFT_ERROR:
+      /* restart transaction */
+      goto retry;
+    case GNUNET_DB_STATUS_SUCCESS_NO_RESULTS:
+      /* Good, we can proceed! */
+      break;
+    case GNUNET_DB_STATUS_SUCCESS_ONE_RESULT:
+      /* idempotency check: is etp == tp? */
+      {
+        bool eq;
+
+        eq = (1 == json_equal (xcategory_name_i18n,
+                               category_name_i18n));
+        json_decref (xcategory_name_i18n);
+        TMH_db->rollback (TMH_db->cls);
+        GNUNET_JSON_parse_free (spec);
+        return eq
+          ? TALER_MHD_REPLY_JSON_PACK (connection,
+                                       MHD_HTTP_OK,
+                                       GNUNET_JSON_pack_uint64 ("category_id",
+                                                                category_id))
+          : TALER_MHD_reply_with_error (connection,
+                                        MHD_HTTP_CONFLICT,
+                                        TALER_EC_MERCHANT_PRIVATE_POST_CATEGORIES_CONFLICT_CATEGORY_EXISTS,
+                                        category_name);
+      }
+    } /* end switch (qs) */
+
+    qs = TMH_db->insert_category (TMH_db->cls,
+                                  mi->settings.id,
+                                  category_name,
+                                  category_name_i18n,
+                                  &category_id);
+    if (GNUNET_DB_STATUS_HARD_ERROR == qs)
+    {
+      TMH_db->rollback (TMH_db->cls);
+      break;
+    }
+    if (GNUNET_DB_STATUS_SUCCESS_ONE_RESULT == qs)
+    {
+      qs = TMH_db->commit (TMH_db->cls);
+      if (GNUNET_DB_STATUS_SOFT_ERROR != qs)
+        break;
+    }
+retry:
+    GNUNET_assert (GNUNET_DB_STATUS_SOFT_ERROR == qs);
+    TMH_db->rollback (TMH_db->cls);
+  } /* for RETRIES loop */
+  GNUNET_JSON_parse_free (spec);
+  if (qs < 0)
+  {
+    GNUNET_break (0);
+    return TALER_MHD_reply_with_error (
+      connection,
+      MHD_HTTP_INTERNAL_SERVER_ERROR,
+      (GNUNET_DB_STATUS_SOFT_ERROR == qs)
+      ? TALER_EC_GENERIC_DB_SOFT_FAILURE
+      : TALER_EC_GENERIC_DB_COMMIT_FAILED,
+      NULL);
+  }
+  return TALER_MHD_REPLY_JSON_PACK (
+    connection,
+    MHD_HTTP_OK,
+    GNUNET_JSON_pack_uint64 ("category_id",
+                             category_id));
+}
+
+
+/* end of taler-merchant-httpd_private-post-categories.c */
diff --git a/src/backend/taler-merchant-httpd_private-post-categories.h b/src/backend/taler-merchant-httpd_private-post-categories.h
new file mode 100644
index 00000000..a8431059
--- /dev/null
+++ b/src/backend/taler-merchant-httpd_private-post-categories.h
@@ -0,0 +1,45 @@
+/*
+  This file is part of TALER
+  (C) 2024 Taler Systems SA
+
+  TALER is free software; you can redistribute it and/or modify
+  it under the terms of the GNU Affero General Public License as
+  published by the Free Software Foundation; either version 3,
+  or (at your option) any later version.
+
+  TALER is distributed in the hope that it will be useful, but
+  WITHOUT ANY WARRANTY; without even the implied warranty of
+  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+  GNU General Public License for more details.
+
+  You should have received a copy of the GNU General Public
+  License along with TALER; see the file COPYING.  If not,
+  see <http://www.gnu.org/licenses/>
+*/
+
+/**
+ * @file taler-merchant-httpd_private-post-categories.h
+ * @brief implementing POST /categories request handling
+ * @author Christian Grothoff
+ */
+#ifndef TALER_MERCHANT_HTTPD_PRIVATE_POST_CATEGORIES_H
+#define TALER_MERCHANT_HTTPD_PRIVATE_POST_CATEGORIES_H
+
+#include "taler-merchant-httpd.h"
+
+
+/**
+ * Generate a product category.
+ *
+ * @param rh context of the handler
+ * @param connection the MHD connection to handle
+ * @param[in,out] hc context with further information about the request
+ * @return MHD result code
+ */
+MHD_RESULT
+TMH_private_post_categories (
+  const struct TMH_RequestHandler *rh,
+  struct MHD_Connection *connection,
+  struct TMH_HandlerContext *hc);
+
+#endif
diff --git a/src/backend/taler-merchant-httpd_private-post-instances.c b/src/backend/taler-merchant-httpd_private-post-instances.c
index a4cf884d..f56e7098 100644
--- a/src/backend/taler-merchant-httpd_private-post-instances.c
+++ b/src/backend/taler-merchant-httpd_private-post-instances.c
@@ -103,20 +103,6 @@ TMH_private_post_instances (const struct TMH_RequestHandler *rh,
              ? MHD_YES
              : MHD_NO;
   }
-  if (NULL == uts)
-    uts = "business";
-  if (GNUNET_OK !=
-      TALER_KYCLOGIC_kyc_user_type_from_string (uts,
-                                                &is.ut))
-  {
-    GNUNET_break_op (0);
-    GNUNET_JSON_parse_free (spec);
-    return TALER_MHD_reply_with_error (connection,
-                                       MHD_HTTP_BAD_REQUEST,
-                                       TALER_EC_GENERIC_PARAMETER_MALFORMED,
-                                       "user_type");
-  }
-
   {
     enum GNUNET_GenericReturnValue ret;
 
diff --git a/src/backend/taler-merchant-httpd_private-post-orders.c b/src/backend/taler-merchant-httpd_private-post-orders.c
index e8332c70..a2e3b493 100644
--- a/src/backend/taler-merchant-httpd_private-post-orders.c
+++ b/src/backend/taler-merchant-httpd_private-post-orders.c
@@ -960,6 +960,8 @@ execute_order (struct OrderContext *oc)
     struct TALER_MERCHANTDB_ProductDetails pd;
     MHD_RESULT ret;
     const struct InventoryProduct *ip;
+    size_t num_categories = 0;
+    uint64_t *categories = NULL;
 
     ip = &oc->parse_request.inventory_products[
       oc->execute_order.out_of_stock_index];
@@ -970,10 +972,13 @@ execute_order (struct OrderContext *oc)
       TMH_db->cls,
       oc->hc->instance->settings.id,
       ip->product_id,
-      &pd);
+      &pd,
+      &num_categories,
+      &categories);
     switch (qs)
     {
     case GNUNET_DB_STATUS_SUCCESS_ONE_RESULT:
+      GNUNET_free (categories);
       GNUNET_log (GNUNET_ERROR_TYPE_INFO,
                   "Order creation failed: product out of stock\n");
       ret = TALER_MHD_REPLY_JSON_PACK (
@@ -1337,6 +1342,7 @@ get_exchange_keys (void *cls,
                                         rx);
 }
 
+
 /**
  * Get rounded time interval. @a start is calculated by rounding
  * @a ts down to the nearest multiple of @a precision. @a end is
@@ -1449,9 +1455,7 @@ set_token_family (struct OrderContext *oc,
   struct TALER_MERCHANTDB_TokenFamilyKeyDetails key_details;
   struct TALER_MerchantContractTokenFamily *family = NULL;
   enum GNUNET_DB_QueryStatus qs;
-  // TODO: make this configurable. This is the granularity of token
-  //       expiration dates. This should be stored in the
-  //       database along the token family.
+  /* TODO: Implement rounding duration of token family and use this here. */
   struct GNUNET_TIME_Relative precision = GNUNET_TIME_UNIT_MONTHS;
   struct GNUNET_TIME_Timestamp min_valid_after;
   struct GNUNET_TIME_Timestamp max_valid_after;
@@ -1694,6 +1698,7 @@ set_token_family (struct OrderContext *oc,
   return GNUNET_OK;
 }
 
+
 /**
  * Serialize order into @a oc->serialize_order.contract,
  * ready to be stored in the database. Upon success, continue
@@ -1712,16 +1717,16 @@ serialize_order (struct OrderContext *oc)
 
   merchant = GNUNET_JSON_PACK (
     GNUNET_JSON_pack_string ("name",
-                              settings->name),
+                             settings->name),
     GNUNET_JSON_pack_allow_null (
       GNUNET_JSON_pack_string ("website",
-                                settings->website)),
+                               settings->website)),
     GNUNET_JSON_pack_allow_null (
       GNUNET_JSON_pack_string ("email",
-                                settings->email)),
+                               settings->email)),
     GNUNET_JSON_pack_allow_null (
       GNUNET_JSON_pack_string ("logo",
-                                settings->logo)));
+                               settings->logo)));
   GNUNET_assert (NULL != merchant);
   {
     json_t *loca;
@@ -1733,7 +1738,7 @@ serialize_order (struct OrderContext *oc)
       loca = json_deep_copy (loca);
       GNUNET_assert (NULL != loca);
       GNUNET_assert (0 ==
-                      json_object_set_new (merchant,
+                     json_object_set_new (merchant,
                                           "address",
                                           loca));
     }
@@ -1748,7 +1753,7 @@ serialize_order (struct OrderContext *oc)
       juri = json_deep_copy (juri);
       GNUNET_assert (NULL != juri);
       GNUNET_assert (0 ==
-                      json_object_set_new (merchant,
+                     json_object_set_new (merchant,
                                           "jurisdiction",
                                           juri));
     }
@@ -1855,10 +1860,10 @@ serialize_order (struct OrderContext *oc)
 
     json_t *jchoice = GNUNET_JSON_PACK (
       GNUNET_JSON_pack_array_incref ("inputs",
-                                      inputs),
+                                     inputs),
       GNUNET_JSON_pack_array_incref ("outputs",
-                                      outputs)
-    );
+                                     outputs)
+      );
 
     GNUNET_assert (0 == json_array_append (choices, jchoice));
   }
@@ -1879,7 +1884,8 @@ serialize_order (struct OrderContext *oc)
                                oc->parse_order.fulfillment_message)),
     GNUNET_JSON_pack_allow_null (
       GNUNET_JSON_pack_object_incref ("fulfillment_message_i18n",
-                                      oc->parse_order.fulfillment_message_i18n)),
+                                      oc->parse_order.fulfillment_message_i18n))
+    ,
     GNUNET_JSON_pack_allow_null (
       GNUNET_JSON_pack_string ("fulfillment_url",
                                oc->parse_order.fulfillment_url)),
@@ -1961,6 +1967,7 @@ serialize_order (struct OrderContext *oc)
   oc->phase++;
 }
 
+
 /**
  * Set max_fee in @a oc based on STEFAN value if
  * not yet present. Upon success, continue
@@ -1996,6 +2003,7 @@ set_max_fee (struct OrderContext *oc)
   oc->phase++;
 }
 
+
 /**
  * Set list of acceptable exchanges in @a oc. Upon success, continue
  * processing with set_max_fee().
@@ -2119,7 +2127,7 @@ parse_order (struct OrderContext *oc)
       NULL),
     GNUNET_JSON_spec_mark_optional (
       GNUNET_JSON_spec_array_const ("choices",
-                                   &oc->parse_order.choices),
+                                    &oc->parse_order.choices),
       NULL),
     GNUNET_JSON_spec_mark_optional (
       TALER_JSON_spec_web_url ("merchant_base_url",
@@ -2185,7 +2193,7 @@ parse_order (struct OrderContext *oc)
                      ret);
     return;
   }
-  if (NULL == version || 0 == strcmp("0", version))
+  if (NULL == version || 0 == strcmp ("0", version))
   {
     oc->parse_order.version = TALER_MCV_V0;
 
@@ -2200,11 +2208,11 @@ parse_order (struct OrderContext *oc)
       return;
     }
   }
-  else if (0 == strcmp("1", version))
+  else if (0 == strcmp ("1", version))
   {
     oc->parse_order.version = TALER_MCV_V1;
 
-    if (! json_is_array(oc->parse_order.choices))
+    if (! json_is_array (oc->parse_order.choices))
     {
       GNUNET_break_op (0);
       GNUNET_JSON_parse_free (spec);
@@ -2237,9 +2245,9 @@ parse_order (struct OrderContext *oc)
     return;
   }
   if ( (! no_fee) &&
-      (GNUNET_OK !=
-       TALER_amount_cmp_currency (&oc->parse_order.brutto,
-                                  &oc->parse_order.max_fee)) )
+       (GNUNET_OK !=
+        TALER_amount_cmp_currency (&oc->parse_order.brutto,
+                                   &oc->parse_order.max_fee)) )
   {
     GNUNET_break_op (0);
     GNUNET_JSON_parse_free (spec);
@@ -2516,6 +2524,7 @@ parse_order (struct OrderContext *oc)
   oc->phase++;
 }
 
+
 /**
  * Parse contract choices. Upon success, continue
  * processing with merge_inventory().
@@ -2606,7 +2615,7 @@ parse_choices (struct OrderContext *oc)
             GNUNET_JSON_spec_uint32 ("count",
                                      &input.details.token.count),
             NULL),
-          GNUNET_JSON_spec_end()
+          GNUNET_JSON_spec_end ()
         };
 
         if (GNUNET_OK !=
@@ -2665,7 +2674,8 @@ parse_choices (struct OrderContext *oc)
       size_t idx;
       json_array_foreach ((json_t *) joutputs, idx, joutput)
       {
-        struct TALER_MerchantContractOutput output = { .details.token.count = 1 };
+        struct TALER_MerchantContractOutput output = { .details.token.count = 1}
+        ;
         const char *kind;
         const char *ierror_name;
         unsigned int ierror_line;
@@ -2682,14 +2692,14 @@ parse_choices (struct OrderContext *oc)
             GNUNET_JSON_spec_uint32 ("count",
                                      &output.details.token.count),
             NULL),
-          GNUNET_JSON_spec_end()
+          GNUNET_JSON_spec_end ()
         };
 
         if (GNUNET_OK !=
             GNUNET_JSON_parse (joutput,
-                              ispec,
-                              &ierror_name,
-                              &ierror_line))
+                               ispec,
+                               &ierror_name,
+                               &ierror_line))
         {
           GNUNET_JSON_parse_free (spec);
           GNUNET_JSON_parse_free (ispec);
@@ -2744,6 +2754,7 @@ parse_choices (struct OrderContext *oc)
   oc->phase++;
 }
 
+
 /**
  * Process the @a payment_target and add the details of how the
  * order could be paid to @a order. On success, continue
@@ -2809,11 +2820,15 @@ merge_inventory (struct OrderContext *oc)
         = &oc->parse_request.inventory_products[i];
       struct TALER_MERCHANTDB_ProductDetails pd;
       enum GNUNET_DB_QueryStatus qs;
+      size_t num_categories = 0;
+      uint64_t *categories = NULL;
 
       qs = TMH_db->lookup_product (TMH_db->cls,
                                    oc->hc->instance->settings.id,
                                    ip->product_id,
-                                   &pd);
+                                   &pd,
+                                   &num_categories,
+                                   &categories);
       if (qs <= 0)
       {
         enum TALER_ErrorCode ec = TALER_EC_GENERIC_INTERNAL_INVARIANT_FAILURE;
@@ -2848,6 +2863,7 @@ merge_inventory (struct OrderContext *oc)
                           ip->product_id);
         return;
       }
+      GNUNET_free (categories);
       oc->parse_order.minimum_age
         = GNUNET_MAX (oc->parse_order.minimum_age,
                       pd.minimum_age);
diff --git a/src/backend/taler-merchant-httpd_private-post-products-ID-lock.c b/src/backend/taler-merchant-httpd_private-post-products-ID-lock.c
index 184f1d28..844b2ec8 100644
--- a/src/backend/taler-merchant-httpd_private-post-products-ID-lock.c
+++ b/src/backend/taler-merchant-httpd_private-post-products-ID-lock.c
@@ -29,9 +29,10 @@
 
 
 MHD_RESULT
-TMH_private_post_products_ID_lock (const struct TMH_RequestHandler *rh,
-                                   struct MHD_Connection *connection,
-                                   struct TMH_HandlerContext *hc)
+TMH_private_post_products_ID_lock (
+  const struct TMH_RequestHandler *rh,
+  struct MHD_Connection *connection,
+  struct TMH_HandlerContext *hc)
 {
   struct TMH_MerchantInstance *mi = hc->instance;
   const char *product_id = hc->infix;
@@ -75,35 +76,48 @@ TMH_private_post_products_ID_lock (const struct TMH_RequestHandler *rh,
   switch (qs)
   {
   case GNUNET_DB_STATUS_HARD_ERROR:
-    return TALER_MHD_reply_with_error (connection,
-                                       MHD_HTTP_INTERNAL_SERVER_ERROR,
-                                       TALER_EC_GENERIC_DB_STORE_FAILED,
-                                       NULL);
+    return TALER_MHD_reply_with_error (
+      connection,
+      MHD_HTTP_INTERNAL_SERVER_ERROR,
+      TALER_EC_GENERIC_DB_STORE_FAILED,
+      NULL);
   case GNUNET_DB_STATUS_SOFT_ERROR:
     GNUNET_break (0);
-    return TALER_MHD_reply_with_error (connection,
-                                       MHD_HTTP_INTERNAL_SERVER_ERROR,
-                                       TALER_EC_GENERIC_INTERNAL_INVARIANT_FAILURE,
-                                       "Serialization error for single-statment request");
+    return TALER_MHD_reply_with_error (
+      connection,
+      MHD_HTTP_INTERNAL_SERVER_ERROR,
+      TALER_EC_GENERIC_INTERNAL_INVARIANT_FAILURE,
+      "Serialization error for single-statment request");
   case GNUNET_DB_STATUS_SUCCESS_NO_RESULTS:
-    qs = TMH_db->lookup_product (TMH_db->cls,
-                                 mi->settings.id,
-                                 product_id,
-                                 NULL);
-    if (GNUNET_DB_STATUS_HARD_ERROR == qs)
-      return TALER_MHD_reply_with_error (connection,
-                                         MHD_HTTP_INTERNAL_SERVER_ERROR,
-                                         TALER_EC_GENERIC_DB_STORE_FAILED,
-                                         "lookup_product");
-    if (GNUNET_DB_STATUS_SUCCESS_NO_RESULTS == qs)
-      return TALER_MHD_reply_with_error (connection,
-                                         MHD_HTTP_NOT_FOUND,
-                                         TALER_EC_MERCHANT_GENERIC_PRODUCT_UNKNOWN,
-                                         product_id);
-    return TALER_MHD_reply_with_error (connection,
-                                       MHD_HTTP_GONE,
-                                       TALER_EC_MERCHANT_PRIVATE_POST_PRODUCTS_LOCK_INSUFFICIENT_STOCKS,
-                                       product_id);
+    {
+      size_t num_categories = 0;
+      uint64_t *categories = NULL;
+
+      qs = TMH_db->lookup_product (TMH_db->cls,
+                                   mi->settings.id,
+                                   product_id,
+                                   NULL,
+                                   &num_categories,
+                                   &categories);
+      if (GNUNET_DB_STATUS_HARD_ERROR == qs)
+        return TALER_MHD_reply_with_error (
+          connection,
+          MHD_HTTP_INTERNAL_SERVER_ERROR,
+          TALER_EC_GENERIC_DB_STORE_FAILED,
+          "lookup_product");
+      if (GNUNET_DB_STATUS_SUCCESS_NO_RESULTS == qs)
+        return TALER_MHD_reply_with_error (
+          connection,
+          MHD_HTTP_NOT_FOUND,
+          TALER_EC_MERCHANT_GENERIC_PRODUCT_UNKNOWN,
+          product_id);
+      GNUNET_free (categories);
+    }
+    return TALER_MHD_reply_with_error (
+      connection,
+      MHD_HTTP_GONE,
+      TALER_EC_MERCHANT_PRIVATE_POST_PRODUCTS_LOCK_INSUFFICIENT_STOCKS,
+      product_id);
   case GNUNET_DB_STATUS_SUCCESS_ONE_RESULT:
     return TALER_MHD_reply_static (connection,
                                    MHD_HTTP_NO_CONTENT,
diff --git a/src/backend/taler-merchant-httpd_private-post-products.c b/src/backend/taler-merchant-httpd_private-post-products.c
index 3cad91a9..3edc0c16 100644
--- a/src/backend/taler-merchant-httpd_private-post-products.c
+++ b/src/backend/taler-merchant-httpd_private-post-products.c
@@ -1,6 +1,6 @@
 /*
   This file is part of TALER
-  (C) 2020 Taler Systems SA
+  (C) 2020-2024 Taler Systems SA
 
   TALER is free software; you can redistribute it and/or modify
   it under the terms of the GNU Affero General Public License as
@@ -28,50 +28,6 @@
 #include <taler/taler_json_lib.h>
 
 
-/**
- * How often do we retry the simple INSERT database transaction?
- */
-#define MAX_RETRIES 3
-
-
-/**
- * Check if the two products are identical.
- *
- * @param p1 product to compare
- * @param p2 other product to compare
- * @return true if they are 'equal', false if not or of payto_uris is not an array
- */
-static bool
-products_equal (const struct TALER_MERCHANTDB_ProductDetails *p1,
-                const struct TALER_MERCHANTDB_ProductDetails *p2)
-{
-  return ( (0 == strcmp (p1->description,
-                         p2->description)) &&
-           (1 == json_equal (p1->description_i18n,
-                             p2->description_i18n)) &&
-           (0 == strcmp (p1->unit,
-                         p2->unit)) &&
-           (GNUNET_OK ==
-            TALER_amount_cmp_currency (&p1->price,
-                                       &p2->price)) &&
-           (0 == TALER_amount_cmp (&p1->price,
-                                   &p2->price)) &&
-           (1 == json_equal (p1->taxes,
-                             p2->taxes)) &&
-           (p1->total_stock == p2->total_stock) &&
-           (p1->total_sold == p2->total_sold) &&
-           (p1->total_lost == p2->total_lost) &&
-           (p1->minimum_age == p2->minimum_age) &&
-           (0 == strcmp (p1->image,
-                         p2->image)) &&
-           (1 == json_equal (p1->address,
-                             p2->address)) &&
-           (GNUNET_TIME_timestamp_cmp (p1->next_restock,
-                                       ==,
-                                       p2->next_restock) ) );
-}
-
-
 MHD_RESULT
 TMH_private_post_products (const struct TMH_RequestHandler *rh,
                            struct MHD_Connection *connection,
@@ -79,9 +35,9 @@ TMH_private_post_products (const struct TMH_RequestHandler *rh,
 {
   struct TMH_MerchantInstance *mi = hc->instance;
   struct TALER_MERCHANTDB_ProductDetails pd = { 0 };
+  const json_t *categories = NULL;
   const char *product_id;
   int64_t total_stock;
-  enum GNUNET_DB_QueryStatus qs;
   struct GNUNET_JSON_Specification spec[] = {
     GNUNET_JSON_spec_string ("product_id",
                              &product_id),
@@ -103,6 +59,10 @@ TMH_private_post_products (const struct TMH_RequestHandler *rh,
       GNUNET_JSON_spec_json ("taxes",
                              &pd.taxes),
       NULL),
+    GNUNET_JSON_spec_mark_optional (
+      GNUNET_JSON_spec_array_const ("categories",
+                                    &categories),
+      NULL),
     GNUNET_JSON_spec_int64 ("total_stock",
                             &total_stock),
     GNUNET_JSON_spec_mark_optional (
@@ -119,6 +79,13 @@ TMH_private_post_products (const struct TMH_RequestHandler *rh,
       NULL),
     GNUNET_JSON_spec_end ()
   };
+  size_t num_cats = 0;
+  uint64_t *cats = NULL;
+  bool conflict;
+  bool no_instance;
+  ssize_t no_cat;
+  enum GNUNET_DB_QueryStatus qs;
+  MHD_RESULT ret;
 
   GNUNET_assert (NULL != mi);
   {
@@ -138,13 +105,33 @@ TMH_private_post_products (const struct TMH_RequestHandler *rh,
   if (total_stock < -1)
   {
     GNUNET_break_op (0);
-    GNUNET_JSON_parse_free (spec);
-    return TALER_MHD_reply_with_error (connection,
-                                       MHD_HTTP_BAD_REQUEST,
-                                       TALER_EC_GENERIC_PARAMETER_MALFORMED,
-                                       "total_stock");
+    ret = TALER_MHD_reply_with_error (connection,
+                                      MHD_HTTP_BAD_REQUEST,
+                                      TALER_EC_GENERIC_PARAMETER_MALFORMED,
+                                      "total_stock");
+    goto cleanup;
   }
+  num_cats = json_array_size (categories);
+  cats = GNUNET_new_array (num_cats,
+                           uint64_t);
+  {
+    size_t idx;
+    json_t *val;
 
+    json_array_foreach (categories, idx, val)
+    {
+      if (! json_is_integer (val))
+      {
+        GNUNET_break_op (0);
+        ret = TALER_MHD_reply_with_error (connection,
+                                          MHD_HTTP_BAD_REQUEST,
+                                          TALER_EC_GENERIC_PARAMETER_MALFORMED,
+                                          "categories");
+        goto cleanup;
+      }
+      cats[idx] = json_integer_value (val);
+    }
+  }
 
   if (-1 == total_stock)
     pd.total_stock = INT64_MAX;
@@ -162,31 +149,31 @@ TMH_private_post_products (const struct TMH_RequestHandler *rh,
   if (! TMH_taxes_array_valid (pd.taxes))
   {
     GNUNET_break_op (0);
-    GNUNET_JSON_parse_free (spec);
-    return TALER_MHD_reply_with_error (connection,
-                                       MHD_HTTP_BAD_REQUEST,
-                                       TALER_EC_GENERIC_PARAMETER_MALFORMED,
-                                       "taxes");
+    ret = TALER_MHD_reply_with_error (connection,
+                                      MHD_HTTP_BAD_REQUEST,
+                                      TALER_EC_GENERIC_PARAMETER_MALFORMED,
+                                      "taxes");
+    goto cleanup;
   }
 
   if (! TMH_location_object_valid (pd.address))
   {
     GNUNET_break_op (0);
-    GNUNET_JSON_parse_free (spec);
-    return TALER_MHD_reply_with_error (connection,
-                                       MHD_HTTP_BAD_REQUEST,
-                                       TALER_EC_GENERIC_PARAMETER_MALFORMED,
-                                       "address");
+    ret = TALER_MHD_reply_with_error (connection,
+                                      MHD_HTTP_BAD_REQUEST,
+                                      TALER_EC_GENERIC_PARAMETER_MALFORMED,
+                                      "address");
+    goto cleanup;
   }
 
   if (! TALER_JSON_check_i18n (pd.description_i18n))
   {
     GNUNET_break_op (0);
-    GNUNET_JSON_parse_free (spec);
-    return TALER_MHD_reply_with_error (connection,
-                                       MHD_HTTP_BAD_REQUEST,
-                                       TALER_EC_GENERIC_PARAMETER_MALFORMED,
-                                       "description_i18n");
+    ret = TALER_MHD_reply_with_error (connection,
+                                      MHD_HTTP_BAD_REQUEST,
+                                      TALER_EC_GENERIC_PARAMETER_MALFORMED,
+                                      "description_i18n");
+    goto cleanup;
   }
 
   if (NULL == pd.image)
@@ -194,110 +181,88 @@ TMH_private_post_products (const struct TMH_RequestHandler *rh,
   if (! TMH_image_data_url_valid (pd.image))
   {
     GNUNET_break_op (0);
-    GNUNET_JSON_parse_free (spec);
-    return TALER_MHD_reply_with_error (connection,
-                                       MHD_HTTP_BAD_REQUEST,
-                                       TALER_EC_GENERIC_PARAMETER_MALFORMED,
-                                       "image");
+    ret = TALER_MHD_reply_with_error (connection,
+                                      MHD_HTTP_BAD_REQUEST,
+                                      TALER_EC_GENERIC_PARAMETER_MALFORMED,
+                                      "image");
+    goto cleanup;
   }
 
-  /* finally, interact with DB until no serialization error */
-  for (unsigned int i = 0; i<MAX_RETRIES; i++)
+  qs = TMH_db->insert_product (TMH_db->cls,
+                               mi->settings.id,
+                               product_id,
+                               &pd,
+                               num_cats,
+                               cats,
+                               &no_instance,
+                               &conflict,
+                               &no_cat);
+  switch (qs)
   {
-    /* Test if an product of this id is known */
-    struct TALER_MERCHANTDB_ProductDetails epd;
-
-    if (GNUNET_OK !=
-        TMH_db->start (TMH_db->cls,
-                       "/post products"))
-    {
-      GNUNET_break (0);
-      GNUNET_JSON_parse_free (spec);
-      return TALER_MHD_reply_with_error (connection,
-                                         MHD_HTTP_INTERNAL_SERVER_ERROR,
-                                         TALER_EC_GENERIC_DB_START_FAILED,
-                                         NULL);
-    }
-    qs = TMH_db->lookup_product (TMH_db->cls,
-                                 mi->settings.id,
-                                 product_id,
-                                 &epd);
-    switch (qs)
-    {
-    case GNUNET_DB_STATUS_HARD_ERROR:
-      /* Clean up and fail hard */
-      GNUNET_break (0);
-      TMH_db->rollback (TMH_db->cls);
-      GNUNET_JSON_parse_free (spec);
-      return TALER_MHD_reply_with_error (connection,
-                                         MHD_HTTP_INTERNAL_SERVER_ERROR,
-                                         TALER_EC_GENERIC_DB_FETCH_FAILED,
-                                         NULL);
-    case GNUNET_DB_STATUS_SOFT_ERROR:
-      /* restart transaction */
-      goto retry;
-    case GNUNET_DB_STATUS_SUCCESS_NO_RESULTS:
-      /* Good, we can proceed! */
-      break;
-    case GNUNET_DB_STATUS_SUCCESS_ONE_RESULT:
-      /* idempotency check: is epd == pd? */
-      {
-        bool eq;
-
-        eq = products_equal (&pd,
-                             &epd);
-        TALER_MERCHANTDB_product_details_free (&epd);
-        TMH_db->rollback (TMH_db->cls);
-        GNUNET_JSON_parse_free (spec);
-        return eq
-          ? TALER_MHD_reply_static (connection,
-                                    MHD_HTTP_NO_CONTENT,
-                                    NULL,
-                                    NULL,
-                                    0)
-          : TALER_MHD_reply_with_error (connection,
-                                        MHD_HTTP_CONFLICT,
-                                        TALER_EC_MERCHANT_PRIVATE_POST_PRODUCTS_CONFLICT_PRODUCT_EXISTS,
-                                        product_id);
-      }
-    } /* end switch (qs) */
-
-    qs = TMH_db->insert_product (TMH_db->cls,
-                                 mi->settings.id,
-                                 product_id,
-                                 &pd);
-    if (GNUNET_DB_STATUS_HARD_ERROR == qs)
-    {
-      TMH_db->rollback (TMH_db->cls);
-      break;
-    }
-    if (GNUNET_DB_STATUS_SUCCESS_ONE_RESULT == qs)
-    {
-      qs = TMH_db->commit (TMH_db->cls);
-      if (GNUNET_DB_STATUS_SOFT_ERROR != qs)
-        break;
-    }
-retry:
-    GNUNET_assert (GNUNET_DB_STATUS_SOFT_ERROR == qs);
-    TMH_db->rollback (TMH_db->cls);
-  } /* for RETRIES loop */
-  GNUNET_JSON_parse_free (spec);
-  if (qs < 0)
-  {
-    GNUNET_break (0);
-    return TALER_MHD_reply_with_error (
+  case GNUNET_DB_STATUS_HARD_ERROR:
+  case GNUNET_DB_STATUS_SOFT_ERROR:
+    ret = TALER_MHD_reply_with_error (
       connection,
       MHD_HTTP_INTERNAL_SERVER_ERROR,
       (GNUNET_DB_STATUS_SOFT_ERROR == qs)
       ? TALER_EC_GENERIC_DB_SOFT_FAILURE
       : TALER_EC_GENERIC_DB_COMMIT_FAILED,
       NULL);
+    goto cleanup;
+  case GNUNET_DB_STATUS_SUCCESS_NO_RESULTS:
+    ret = TALER_MHD_reply_with_error (
+      connection,
+      MHD_HTTP_INTERNAL_SERVER_ERROR,
+      TALER_EC_GENERIC_DB_INVARIANT_FAILURE,
+      NULL);
+    goto cleanup;
+  case GNUNET_DB_STATUS_SUCCESS_ONE_RESULT:
+    break;
   }
-  return TALER_MHD_reply_static (connection,
-                                 MHD_HTTP_NO_CONTENT,
-                                 NULL,
-                                 NULL,
-                                 0);
+  if (no_instance)
+  {
+    ret = TALER_MHD_reply_with_error (
+      connection,
+      MHD_HTTP_NOT_FOUND,
+      TALER_EC_MERCHANT_GENERIC_INSTANCE_UNKNOWN,
+      mi->settings.id);
+    goto cleanup;
+  }
+  if (conflict)
+  {
+    ret = TALER_MHD_reply_with_error (
+      connection,
+      MHD_HTTP_CONFLICT,
+      TALER_EC_MERCHANT_PRIVATE_POST_PRODUCTS_CONFLICT_PRODUCT_EXISTS,
+      product_id);
+    goto cleanup;
+  }
+  if (-1 != no_cat)
+  {
+    char nocats[24];
+
+    GNUNET_break_op (0);
+    TMH_db->rollback (TMH_db->cls);
+    GNUNET_snprintf (nocats,
+                     sizeof (nocats),
+                     "%llu",
+                     (unsigned long long) no_cat);
+    ret = TALER_MHD_reply_with_error (
+      connection,
+      MHD_HTTP_NOT_FOUND,
+      TALER_EC_MERCHANT_GENERIC_CATEGORY_UNKNOWN,
+      nocats);
+    goto cleanup;
+  }
+  ret = TALER_MHD_reply_static (connection,
+                                MHD_HTTP_NO_CONTENT,
+                                NULL,
+                                NULL,
+                                0);
+cleanup:
+  GNUNET_JSON_parse_free (spec);
+  GNUNET_free (cats);
+  return ret;
 }
 
 
diff --git a/src/backend/taler-merchant-webhook.c b/src/backend/taler-merchant-webhook.c
index 80db78fd..1d17843e 100644
--- a/src/backend/taler-merchant-webhook.c
+++ b/src/backend/taler-merchant-webhook.c
@@ -506,7 +506,7 @@ run (void *cls,
   {
     GNUNET_break (0);
     GNUNET_SCHEDULER_shutdown ();
-    global_ret = EXIT_NO_RESTART;
+    global_ret = EXIT_FAILURE;
     return;
   }
   if (NULL ==
@@ -524,7 +524,7 @@ run (void *cls,
     GNUNET_log (GNUNET_ERROR_TYPE_ERROR,
                 "Failed to connect to database\n");
     GNUNET_SCHEDULER_shutdown ();
-    global_ret = EXIT_NO_RESTART;
+    global_ret = EXIT_FAILURE;
     return;
   }
   {
diff --git a/src/backend/taler-merchant-wirewatch.c b/src/backend/taler-merchant-wirewatch.c
index 17eb7a0a..bba101e3 100644
--- a/src/backend/taler-merchant-wirewatch.c
+++ b/src/backend/taler-merchant-wirewatch.c
@@ -641,7 +641,7 @@ run (void *cls,
   {
     GNUNET_break (0);
     GNUNET_SCHEDULER_shutdown ();
-    global_ret = EXIT_NO_RESTART;
+    global_ret = EXIT_FAILURE;
     return;
   }
   if (NULL ==
@@ -659,7 +659,7 @@ run (void *cls,
     GNUNET_log (GNUNET_ERROR_TYPE_ERROR,
                 "Failed to connect to database\n");
     GNUNET_SCHEDULER_shutdown ();
-    global_ret = EXIT_NO_RESTART;
+    global_ret = EXIT_FAILURE;
     return;
   }
   {
diff --git a/src/backenddb/Makefile.am b/src/backenddb/Makefile.am
index 95efe07e..e6511fef 100644
--- a/src/backenddb/Makefile.am
+++ b/src/backenddb/Makefile.am
@@ -65,7 +65,7 @@ libtalermerchantdb_la_LIBADD = \
 
 libtalermerchantdb_la_LDFLAGS = \
   $(POSTGRESQL_LDFLAGS) \
-  -version-info 3:0:1 \
+  -version-info 4:0:2 \
   -no-undefined
 
 libtaler_plugin_merchantdb_postgres_la_SOURCES = \
@@ -79,6 +79,12 @@ libtaler_plugin_merchantdb_postgres_la_SOURCES = \
   pg_insert_transfer_details.h pg_insert_transfer_details.c \
   pg_store_wire_fee_by_exchange.h pg_store_wire_fee_by_exchange.c \
   pg_select_open_transfers.h pg_select_open_transfers.c \
+  pg_lookup_categories.h pg_lookup_categories.c \
+  pg_select_category_by_name.h pg_select_category_by_name.c \
+  pg_select_category.h pg_select_category.c \
+  pg_update_category.h pg_update_category.c \
+  pg_insert_category.h pg_insert_category.c \
+  pg_delete_category.h pg_delete_category.c \
   pg_lookup_instances.h pg_lookup_instances.c \
   pg_lookup_transfers.h pg_lookup_transfers.c \
   pg_update_transfer_status.h pg_update_transfer_status.c \
@@ -115,6 +121,7 @@ libtaler_plugin_merchantdb_postgres_la_SOURCES = \
   pg_update_template.h pg_update_template.c \
   pg_lookup_templates.h pg_lookup_templates.c \
   pg_lookup_template.h pg_lookup_template.c \
+  pg_lookup_all_products.h pg_lookup_all_products.c \
   pg_lookup_products.h pg_lookup_products.c \
   pg_lookup_product.h pg_lookup_product.c \
   pg_delete_product.h pg_delete_product.c \
diff --git a/src/backenddb/merchant-0001.sql b/src/backenddb/merchant-0001.sql
index 2adb9996..ca753a04 100644
--- a/src/backenddb/merchant-0001.sql
+++ b/src/backenddb/merchant-0001.sql
@@ -194,7 +194,7 @@ CREATE TABLE IF NOT EXISTS merchant_inventory
   ,description TEXT NOT NULL
   ,description_i18n BYTEA NOT NULL
   ,unit TEXT NOT NULL
-  ,image BYTEA NOT NULL
+  ,image BYTEA NOT NULL -- NOTE: merchant-0006 changes this to TEXT!
   ,taxes BYTEA NOT NULL
   ,price taler_amount_currency NOT NULL
   ,total_stock BIGINT NOT NULL
diff --git a/src/backenddb/merchant-0006.sql b/src/backenddb/merchant-0006.sql
index c0059b18..e216b4ad 100644
--- a/src/backenddb/merchant-0006.sql
+++ b/src/backenddb/merchant-0006.sql
@@ -32,5 +32,37 @@ ALTER TABLE merchant_contract_terms
 COMMENT ON COLUMN merchant_contract_terms.choice_index
   IS 'Index of selected choice. Refers to the `choices` array in the contract terms. NULL for contracts without choices.';
 
+ALTER TABLE merchant_inventory
+  ALTER COLUMN image SET DATA TYPE TEXT;
+
+CREATE TABLE IF NOT EXISTS merchant_categories
+  (category_serial BIGINT GENERATED BY DEFAULT AS IDENTITY PRIMARY KEY
+  ,merchant_serial BIGINT NOT NULL
+    REFERENCES merchant_instances (merchant_serial) ON DELETE CASCADE
+  ,category_name TEXT NOT NULL UNIQUE
+  ,category_name_i18n BYTEA NOT NULL
+  );
+
+COMMENT ON COLUMN merchant_categories.category_name
+  IS 'name of the category';
+COMMENT ON COLUMN merchant_categories.category_name_i18n
+  IS 'JSON with translations of the category name';
+
+CREATE TABLE merchant_product_categories
+  (category_serial BIGINT NOT NULL
+    REFERENCES merchant_categories (category_serial) ON DELETE CASCADE
+  ,product_serial BIGINT NOT NULL
+    REFERENCES merchant_inventory (product_serial) ON DELETE CASCADE);
+CREATE INDEX merchant_categories_by_category
+  ON merchant_product_categories (category_serial);
+CREATE INDEX merchant_categories_by_product
+  ON merchant_product_categories (product_serial);
+
+COMMENT ON COLUMN merchant_product_categories.category_serial
+  IS 'Reference to a category the product is part of';
+COMMENT ON COLUMN merchant_product_categories.product_serial
+  IS 'Reference to a product which is in the given category';
+
+
 -- Complete transaction
 COMMIT;
diff --git a/src/backenddb/merchantdb_helper.c b/src/backenddb/merchantdb_helper.c
index 5894525c..6c1d2ec6 100644
--- a/src/backenddb/merchantdb_helper.c
+++ b/src/backenddb/merchantdb_helper.c
@@ -83,4 +83,25 @@ TALER_MERCHANTDB_token_family_details_free (
 }
 
 
+void
+TALER_MERCHANTDB_category_details_free (
+  struct TALER_MERCHANTDB_CategoryDetails *cd)
+{
+  GNUNET_free (cd->category_name);
+  json_decref (cd->category_name_i18n);
+  for (unsigned int i = 0; i<cd->num_products; i++)
+  {
+    struct TALER_MERCHANTDB_ProductSummary *ps
+      = &cd->products[i];
+
+    GNUNET_free (ps->product_id);
+    GNUNET_free (ps->description);
+    json_decref (ps->description_i18n);
+  }
+  GNUNET_array_grow (cd->products,
+                     cd->num_products,
+                     0);
+}
+
+
 /* end of merchantdb_helper.c */
diff --git a/src/backenddb/pg_delete_category.c b/src/backenddb/pg_delete_category.c
new file mode 100644
index 00000000..4a43aa37
--- /dev/null
+++ b/src/backenddb/pg_delete_category.c
@@ -0,0 +1,54 @@
+/*
+   This file is part of TALER
+   Copyright (C) 2024 Taler Systems SA
+
+   TALER is free software; you can redistribute it and/or modify it under the
+   terms of the GNU General Public License as published by the Free Software
+   Foundation; either version 3, or (at your option) any later version.
+
+   TALER is distributed in the hope that it will be useful, but WITHOUT ANY
+   WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR
+   A PARTICULAR PURPOSE.  See the GNU General Public License for more details.
+
+   You should have received a copy of the GNU General Public License along with
+   TALER; see the file COPYING.  If not, see <http://www.gnu.org/licenses/>
+ */
+/**
+ * @file backenddb/pg_delete_category.c
+ * @brief Implementation of the delete_category function for Postgres
+ * @author Christian Grothoff
+ */
+#include "platform.h"
+#include <taler/taler_error_codes.h>
+#include <taler/taler_dbevents.h>
+#include <taler/taler_pq_lib.h>
+#include "pg_delete_category.h"
+#include "pg_helper.h"
+
+
+enum GNUNET_DB_QueryStatus
+TMH_PG_delete_category (void *cls,
+                        const char *instance_id,
+                        uint64_t category_id)
+{
+  struct PostgresClosure *pg = cls;
+  struct GNUNET_PQ_QueryParam params[] = {
+    GNUNET_PQ_query_param_string (instance_id),
+    GNUNET_PQ_query_param_uint64 (&category_id),
+    GNUNET_PQ_query_param_end
+  };
+
+  check_connection (pg);
+  PREPARE (pg,
+           "delete_category",
+           "DELETE"
+           " FROM merchant_categories"
+           " WHERE merchant_serial="
+           "     (SELECT merchant_serial "
+           "        FROM merchant_instances"
+           "        WHERE merchant_id=$1)"
+           "   AND category_serial=$2");
+  return GNUNET_PQ_eval_prepared_non_select (pg->conn,
+                                             "delete_category",
+                                             params);
+}
diff --git a/src/backenddb/pg_delete_category.h b/src/backenddb/pg_delete_category.h
new file mode 100644
index 00000000..8837a6b8
--- /dev/null
+++ b/src/backenddb/pg_delete_category.h
@@ -0,0 +1,43 @@
+/*
+   This file is part of TALER
+   Copyright (C) 2024 Taler Systems SA
+
+   TALER is free software; you can redistribute it and/or modify it under the
+   terms of the GNU General Public License as published by the Free Software
+   Foundation; either version 3, or (at your option) any later version.
+
+   TALER is distributed in the hope that it will be useful, but WITHOUT ANY
+   WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR
+   A PARTICULAR PURPOSE.  See the GNU General Public License for more details.
+
+   You should have received a copy of the GNU General Public License along with
+   TALER; see the file COPYING.  If not, see <http://www.gnu.org/licenses/>
+ */
+/**
+ * @file backenddb/pg_delete_category.h
+ * @brief implementation of the delete_category function for Postgres
+ * @author Christian Grothoff
+ */
+#ifndef PG_DELETE_CATEGORY_H
+#define PG_DELETE_CATEGORY_H
+
+#include <taler/taler_util.h>
+#include <taler/taler_json_lib.h>
+#include "taler_merchantdb_plugin.h"
+
+/**
+ * Delete information about a product category.
+ *
+ * @param cls closure
+ * @param instance_id instance to delete category of
+ * @param category_id identifies the category to delete
+ * @return DB status code, #GNUNET_DB_STATUS_SUCCESS_NO_RESULTS
+ *           if template unknown.
+ */
+enum GNUNET_DB_QueryStatus
+TMH_PG_delete_category (void *cls,
+                        const char *instance_id,
+                        uint64_t category_id);
+
+
+#endif
diff --git a/src/backenddb/pg_delete_otp.c b/src/backenddb/pg_delete_otp.c
index 5f011a4b..60f20481 100644
--- a/src/backenddb/pg_delete_otp.c
+++ b/src/backenddb/pg_delete_otp.c
@@ -43,11 +43,11 @@ TMH_PG_delete_otp (void *cls,
            "delete_otp",
            "DELETE"
            " FROM merchant_otp_devices"
-           " WHERE merchant_otp_devices.merchant_serial="
+           " WHERE merchant_serial="
            "     (SELECT merchant_serial "
            "        FROM merchant_instances"
            "        WHERE merchant_id=$1)"
-           "   AND merchant_otp_devices.otp_id=$2");
+           "   AND otp_id=$2");
   return GNUNET_PQ_eval_prepared_non_select (pg->conn,
                                              "delete_otp",
                                              params);
diff --git a/src/backenddb/pg_insert_category.c b/src/backenddb/pg_insert_category.c
new file mode 100644
index 00000000..f820b2c6
--- /dev/null
+++ b/src/backenddb/pg_insert_category.c
@@ -0,0 +1,65 @@
+/*
+   This file is part of TALER
+   Copyright (C) 2024 Taler Systems SA
+
+   TALER is free software; you can redistribute it and/or modify it under the
+   terms of the GNU General Public License as published by the Free Software
+   Foundation; either version 3, or (at your option) any later version.
+
+   TALER is distributed in the hope that it will be useful, but WITHOUT ANY
+   WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR
+   A PARTICULAR PURPOSE.  See the GNU General Public License for more details.
+
+   You should have received a copy of the GNU General Public License along with
+   TALER; see the file COPYING.  If not, see <http://www.gnu.org/licenses/>
+ */
+/**
+ * @file backenddb/pg_insert_category.c
+ * @brief Implementation of the insert_category function for Postgres
+ * @author Christian Grothoff
+ */
+#include "platform.h"
+#include <taler/taler_error_codes.h>
+#include <taler/taler_dbevents.h>
+#include <taler/taler_pq_lib.h>
+#include "pg_insert_category.h"
+#include "pg_helper.h"
+
+
+enum GNUNET_DB_QueryStatus
+TMH_PG_insert_category (void *cls,
+                        const char *instance_id,
+                        const char *category_name,
+                        const json_t *category_name_i18n,
+                        uint64_t *category_id)
+{
+  struct PostgresClosure *pg = cls;
+  struct GNUNET_PQ_QueryParam params[] = {
+    GNUNET_PQ_query_param_string (instance_id),
+    GNUNET_PQ_query_param_string (category_name),
+    TALER_PQ_query_param_json (category_name_i18n),
+    GNUNET_PQ_query_param_end
+  };
+  struct GNUNET_PQ_ResultSpec rs[] = {
+    GNUNET_PQ_result_spec_uint64 ("category_serial",
+                                  category_id),
+    GNUNET_PQ_result_spec_end
+  };
+
+  check_connection (pg);
+  PREPARE (pg,
+           "insert_category",
+           "INSERT INTO merchant_categories"
+           "(category_name"
+           ",category_name_i18n"
+           ")"
+           " SELECT merchant_serial,"
+           " $2, $3"
+           " FROM merchant_instances"
+           " WHERE merchant_id=$1"
+           " RETURNING category_serial");
+  return GNUNET_PQ_eval_prepared_singleton_select (pg->conn,
+                                                   "insert_category",
+                                                   params,
+                                                   rs);
+}
diff --git a/src/backenddb/pg_insert_category.h b/src/backenddb/pg_insert_category.h
new file mode 100644
index 00000000..8f4bfc99
--- /dev/null
+++ b/src/backenddb/pg_insert_category.h
@@ -0,0 +1,46 @@
+/*
+   This file is part of TALER
+   Copyright (C) 2024 Taler Systems SA
+
+   TALER is free software; you can redistribute it and/or modify it under the
+   terms of the GNU General Public License as published by the Free Software
+   Foundation; either version 3, or (at your option) any later version.
+
+   TALER is distributed in the hope that it will be useful, but WITHOUT ANY
+   WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR
+   A PARTICULAR PURPOSE.  See the GNU General Public License for more details.
+
+   You should have received a copy of the GNU General Public License along with
+   TALER; see the file COPYING.  If not, see <http://www.gnu.org/licenses/>
+ */
+/**
+ * @file backenddb/pg_insert_category.h
+ * @brief implementation of the insert_category function for Postgres
+ * @author Christian Grothoff
+ */
+#ifndef PG_INSERT_CATEGORY_H
+#define PG_INSERT_CATEGORY_H
+
+#include <taler/taler_util.h>
+#include <taler/taler_json_lib.h>
+#include "taler_merchantdb_plugin.h"
+
+/**
+ * Insert new product category.
+ *
+ * @param cls closure
+ * @param instance_id instance to insert OTP device for
+ * @param category_name name of the category
+ * @param category_name_i18n translations of the category name
+ * @param[out] category_id set to the category id on success
+ * @return database result code
+ */
+enum GNUNET_DB_QueryStatus
+TMH_PG_insert_category (void *cls,
+                        const char *instance_id,
+                        const char *category_name,
+                        const json_t *category_name_i18n,
+                        uint64_t *category_id);
+
+
+#endif
diff --git a/src/backenddb/pg_insert_deposit_to_transfer.sql b/src/backenddb/pg_insert_deposit_to_transfer.sql
index b2e587f1..ae43b613 100644
--- a/src/backenddb/pg_insert_deposit_to_transfer.sql
+++ b/src/backenddb/pg_insert_deposit_to_transfer.sql
@@ -114,7 +114,7 @@ SELECT deposit_confirmation_serial
 -- for the entire deposit confirmation
 UPDATE merchant_deposit_confirmations
   SET wire_pending=FALSE
-  WHERE (deposit_confirmation_serial=decose)
+  WHERE (deposit_confirmation_serial=my_decose)
     AND NOT EXISTS
     (SELECT 1
       FROM merchant_deposits md
diff --git a/src/backenddb/pg_insert_instance.c b/src/backenddb/pg_insert_instance.c
index 6928a094..f1217e29 100644
--- a/src/backenddb/pg_insert_instance.c
+++ b/src/backenddb/pg_insert_instance.c
@@ -35,14 +35,12 @@ TMH_PG_insert_instance (
   const struct TALER_MERCHANTDB_InstanceAuthSettings *ias)
 {
   struct PostgresClosure *pg = cls;
-  uint32_t ut32 = (uint32_t) is->ut;
   struct GNUNET_PQ_QueryParam params[] = {
     GNUNET_PQ_query_param_auto_from_type (merchant_pub),
     GNUNET_PQ_query_param_auto_from_type (&ias->auth_hash),
     GNUNET_PQ_query_param_auto_from_type (&ias->auth_salt),
     GNUNET_PQ_query_param_string (is->id),
     GNUNET_PQ_query_param_string (is->name),
-    GNUNET_PQ_query_param_uint32 (&ut32),
     TALER_PQ_query_param_json (is->address),
     TALER_PQ_query_param_json (is->jurisdiction),
     GNUNET_PQ_query_param_bool (is->use_stefan),
@@ -76,7 +74,6 @@ TMH_PG_insert_instance (
            ",auth_salt"
            ",merchant_id"
            ",merchant_name"
-           ",user_type"
            ",address"
            ",jurisdiction"
            ",use_stefan"
@@ -84,9 +81,10 @@ TMH_PG_insert_instance (
            ",default_pay_delay"
            ",website"
            ",email"
-           ",logo)"
+           ",logo"
+           ",user_type)"
            "VALUES"
-           "($1, $2, $3, $4, $5, $6, $7, $8, $9, $10, $11, $12, $13, $14)");
+           "($1, $2, $3, $4, $5, $6, $7, $8, $9, $10, $11, $12, $13, 0)");
   qs = GNUNET_PQ_eval_prepared_non_select (pg->conn,
                                            "insert_instance",
                                            params);
diff --git a/src/backenddb/pg_insert_product.c b/src/backenddb/pg_insert_product.c
index 55db57e9..0d0a8380 100644
--- a/src/backenddb/pg_insert_product.c
+++ b/src/backenddb/pg_insert_product.c
@@ -1,6 +1,6 @@
 /*
    This file is part of TALER
-   Copyright (C) 2022 Taler Systems SA
+   Copyright (C) 2022-2024 Taler Systems SA
 
    TALER is free software; you can redistribute it and/or modify it under the
    terms of the GNU General Public License as published by the Free Software
@@ -30,7 +30,12 @@ enum GNUNET_DB_QueryStatus
 TMH_PG_insert_product (void *cls,
                        const char *instance_id,
                        const char *product_id,
-                       const struct TALER_MERCHANTDB_ProductDetails *pd)
+                       const struct TALER_MERCHANTDB_ProductDetails *pd,
+                       size_t num_cats,
+                       const uint64_t *cats,
+                       bool *no_instance,
+                       bool *conflict,
+                       ssize_t *no_cat)
 {
   struct PostgresClosure *pg = cls;
   struct GNUNET_PQ_QueryParam params[] = {
@@ -42,36 +47,45 @@ TMH_PG_insert_product (void *cls,
     GNUNET_PQ_query_param_string (pd->image),
     TALER_PQ_query_param_json (pd->taxes),
     TALER_PQ_query_param_amount_with_currency (pg->conn,
-                                 &pd->price),
+                                               &pd->price),
     GNUNET_PQ_query_param_uint64 (&pd->total_stock),
     TALER_PQ_query_param_json (pd->address),
     GNUNET_PQ_query_param_timestamp (&pd->next_restock),
     GNUNET_PQ_query_param_uint32 (&pd->minimum_age),
+    GNUNET_PQ_query_param_array_uint64 (num_cats,
+                                        cats,
+                                        pg->conn),
     GNUNET_PQ_query_param_end
   };
+  uint64_t ncat;
+  bool cats_found = true;
+  struct GNUNET_PQ_ResultSpec rs[] = {
+    GNUNET_PQ_result_spec_bool ("conflict",
+                                conflict),
+    GNUNET_PQ_result_spec_bool ("no_instance",
+                                no_instance),
+    GNUNET_PQ_result_spec_allow_null (
+      GNUNET_PQ_result_spec_uint64 ("no_cat",
+                                    &ncat),
+      &cats_found),
+    GNUNET_PQ_result_spec_end
+  };
+  enum GNUNET_DB_QueryStatus qs;
 
   check_connection (pg);
   PREPARE (pg,
            "insert_product",
-           "INSERT INTO merchant_inventory"
-           "(merchant_serial"
-           ",product_id"
-           ",description"
-           ",description_i18n"
-           ",unit"
-           ",image"
-           ",taxes"
-           ",price"
-           ",total_stock"
-           ",address"
-           ",next_restock"
-           ",minimum_age"
-           ")"
-           " SELECT merchant_serial,"
-           " $2, $3, $4, $5, $6, $7, $8, $9, $10, $11, $12"
-           " FROM merchant_instances"
-           " WHERE merchant_id=$1");
-  return GNUNET_PQ_eval_prepared_non_select (pg->conn,
-                                             "insert_product",
-                                             params);
+           "SELECT"
+           " out_conflict AS conflict"
+           ",out_no_cat AS no_cat"
+           ",out_no_instance AS no_instance"
+           " FROM merchant_do_insert_product"
+           "($1, $2, $3, $4, $5, $6, $7, $8, $9, $10, $11, $12, $13);");
+  qs = GNUNET_PQ_eval_prepared_singleton_select (pg->conn,
+                                                 "insert_product",
+                                                 params,
+                                                 rs);
+  GNUNET_PQ_cleanup_query_params_closures (params);
+  *no_cat = (cats_found) ? -1 : (ssize_t) ncat;
+  return qs;
 }
diff --git a/src/backenddb/pg_insert_product.h b/src/backenddb/pg_insert_product.h
index 169bd150..5e85228e 100644
--- a/src/backenddb/pg_insert_product.h
+++ b/src/backenddb/pg_insert_product.h
@@ -32,12 +32,24 @@
  * @param instance_id instance to insert product for
  * @param product_id product identifier of product to insert
  * @param pd the product details to insert
+ * @param num_cats length of @a cats array
+ * @param cats array of categories the product is in
+ * @param[out] no_instance set to true if @a instance_id is unknown
+ * @param[out] conflict set to true if a conflicting
+ *        product already exists in the database
+ * @param[out] no_cat set to index of non-existing category from @a cats, or -1 if all @a cats were found
  * @return database result code
  */
 enum GNUNET_DB_QueryStatus
 TMH_PG_insert_product (void *cls,
                        const char *instance_id,
                        const char *product_id,
-                       const struct TALER_MERCHANTDB_ProductDetails *pd);
+                       const struct TALER_MERCHANTDB_ProductDetails *pd,
+                       size_t num_cats,
+                       const uint64_t *cats,
+                       bool *no_instance,
+                       bool *conflict,
+                       ssize_t *no_cat);
+
 
 #endif
diff --git a/src/backenddb/pg_insert_product.sql b/src/backenddb/pg_insert_product.sql
new file mode 100644
index 00000000..4abf4469
--- /dev/null
+++ b/src/backenddb/pg_insert_product.sql
@@ -0,0 +1,175 @@
+--
+-- This file is part of TALER
+-- Copyright (C) 2024 Taler Systems SA
+--
+-- TALER is free software; you can redistribute it and/or modify it under the
+-- terms of the GNU General Public License as published by the Free Software
+-- Foundation; either version 3, or (at your option) any later version.
+--
+-- TALER is distributed in the hope that it will be useful, but WITHOUT ANY
+-- WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR
+-- A PARTICULAR PURPOSE.  See the GNU General Public License for more details.
+--
+-- You should have received a copy of the GNU General Public License along with
+-- TALER; see the file COPYING.  If not, see <http://www.gnu.org/licenses/>
+--
+
+
+CREATE OR REPLACE FUNCTION merchant_do_insert_product (
+  IN in_instance_id TEXT,
+  IN in_product_id TEXT,
+  IN in_description TEXT,
+  IN in_description_i18n BYTEA,
+  IN in_unit TEXT,
+  IN in_image TEXT,
+  IN in_taxes BYTEA,
+  IN in_price taler_amount_currency,
+  IN in_total_stock INT8,
+  IN in_address BYTEA,
+  IN in_next_restock INT8,
+  IN in_minimum_age INT4,
+  IN ina_categories INT8[],
+  OUT out_no_instance BOOL,
+  OUT out_conflict BOOL,
+  OUT out_no_cat INT8)
+LANGUAGE plpgsql
+AS $$
+DECLARE
+  my_merchant_id INT8;
+  my_product_serial INT8;
+  i INT8;
+  ini_cat INT8;
+BEGIN
+
+-- Which instance are we using?
+SELECT merchant_serial
+  INTO my_merchant_id
+  FROM merchant_instances
+ WHERE merchant_id=in_instance_id;
+
+IF NOT FOUND
+THEN
+  out_no_instance=TRUE;
+  out_conflict=FALSE;
+  out_no_cat=NULL;
+  RETURN;
+END IF;
+out_no_instance=FALSE;
+
+INSERT INTO merchant_inventory
+ (merchant_serial
+ ,product_id
+ ,description
+ ,description_i18n
+ ,unit
+ ,image
+ ,taxes
+ ,price
+ ,total_stock
+ ,address
+ ,next_restock
+ ,minimum_age
+) VALUES (
+  my_merchant_id
+ ,in_product_id
+ ,in_description
+ ,in_description_i18n
+ ,in_unit
+ ,in_image
+ ,in_taxes
+ ,in_price
+ ,in_total_stock
+ ,in_address
+ ,in_next_restock
+ ,in_minimum_age)
+ON CONFLICT (merchant_serial, product_id) DO NOTHING
+ RETURNING product_serial
+ INTO my_product_serial;
+
+
+IF NOT FOUND
+THEN
+  -- Check for idempotency
+  SELECT product_serial
+    INTO my_product_serial
+    FROM merchant_inventory
+  WHERE merchant_serial=my_merchant_id
+    AND product_id=in_product_id
+    AND description=in_description
+    AND description_i18n=in_description_i18n
+    AND unit=in_unit
+    AND image=in_image
+    AND taxes=in_taxes
+    AND price=in_price
+    AND total_stock=in_total_stock
+    AND address=in_address
+    AND next_restock=in_next_restock
+    AND minimum_age=in_minimum_age;
+  IF NOT FOUND
+  THEN
+    out_conflict=TRUE;
+    out_no_cat=NULL;
+    RETURN;
+  END IF;
+
+  -- Check categories match as well
+  FOR i IN 1..COALESCE(array_length(ina_categories,1),0)
+  LOOP
+    ini_cat=ina_categories[i];
+
+    PERFORM
+      FROM merchant_product_categories
+      WHERE product_serial=my_product_serial
+        AND category_serial=ini_cat;
+    IF NOT FOUND
+    THEN
+      out_conflict=TRUE;
+      out_no_cat=NULL;
+      RETURN;
+    END IF;
+  END LOOP;
+
+  -- Also check there are no additional categories
+  -- in either set.
+  SELECT COUNT(*)
+    INTO i
+    FROM merchant_product_categories
+    WHERE product_serial=my_product_serial;
+  IF i != array_length(ina_categories,1)
+  THEN
+    out_conflict=TRUE;
+    out_no_cat=NULL;
+    RETURN;
+  END IF;
+
+  -- Is idempotent!
+  out_conflict=FALSE;
+  out_no_cat=NULL;
+  RETURN;
+END IF;
+out_conflict=FALSE;
+
+
+-- Add categories
+FOR i IN 1..COALESCE(array_length(ina_categories,1),0)
+LOOP
+  ini_cat=ina_categories[i];
+
+  INSERT INTO merchant_product_categories
+   (product_serial
+   ,category_serial)
+  VALUES
+   (my_product_serial
+   ,ini_cat)
+  ON CONFLICT DO NOTHING;
+
+  IF NOT FOUND
+  THEN
+    out_no_cat=i;
+    RETURN;
+  END IF;
+END LOOP;
+
+-- Success!
+out_no_cat=NULL;
+END $$;
diff --git a/src/backenddb/pg_lookup_all_products.c b/src/backenddb/pg_lookup_all_products.c
new file mode 100644
index 00000000..31320d59
--- /dev/null
+++ b/src/backenddb/pg_lookup_all_products.c
@@ -0,0 +1,193 @@
+/*
+   This file is part of TALER
+   Copyright (C) 2024 Taler Systems SA
+
+   TALER is free software; you can redistribute it and/or modify it under the
+   terms of the GNU General Public License as published by the Free Software
+   Foundation; either version 3, or (at your option) any later version.
+
+   TALER is distributed in the hope that it will be useful, but WITHOUT ANY
+   WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR
+   A PARTICULAR PURPOSE.  See the GNU General Public License for more details.
+
+   You should have received a copy of the GNU General Public License along with
+   TALER; see the file COPYING.  If not, see <http://www.gnu.org/licenses/>
+ */
+/**
+ * @file backenddb/pg_lookup_all_products.c
+ * @brief Implementation of the lookup_all_products function for Postgres
+ * @author Christian Grothoff
+ */
+#include "platform.h"
+#include <taler/taler_error_codes.h>
+#include <taler/taler_dbevents.h>
+#include <taler/taler_pq_lib.h>
+#include "pg_lookup_products.h"
+#include "pg_helper.h"
+
+/**
+ * Context used for TMH_PG_lookup_all_products().
+ */
+struct LookupProductsContext
+{
+  /**
+   * Function to call with the results.
+   */
+  TALER_MERCHANTDB_ProductCallback cb;
+
+  /**
+   * Closure for @a cb.
+   */
+  void *cb_cls;
+
+  /**
+   * Postgres context.
+   */
+  struct PostgresClosure *pg;
+
+  /**
+   * Did database result extraction fail?
+   */
+  bool extract_failed;
+};
+
+
+/**
+ * Function to be called with the results of a SELECT statement
+ * that has returned @a num_results results about products.
+ *
+ * @param[in,out] cls of type `struct LookupProductsContext *`
+ * @param result the postgres result
+ * @param num_results the number of results in @a result
+ */
+static void
+lookup_products_cb (void *cls,
+                    PGresult *result,
+                    unsigned int num_results)
+{
+  struct LookupProductsContext *plc = cls;
+  struct PostgresClosure *pg = plc->pg;
+
+  for (unsigned int i = 0; i < num_results; i++)
+  {
+    char *product_id;
+    uint64_t product_serial;
+    struct TALER_MERCHANTDB_ProductDetails pd;
+    size_t num_categories;
+    uint64_t *categories;
+    struct GNUNET_PQ_ResultSpec rs[] = {
+      GNUNET_PQ_result_spec_string ("product_id",
+                                    &product_id),
+      GNUNET_PQ_result_spec_uint64 ("product_serial",
+                                    &product_serial),
+      GNUNET_PQ_result_spec_string ("description",
+                                    &pd.description),
+      TALER_PQ_result_spec_json ("description_i18n",
+                                 &pd.description_i18n),
+      GNUNET_PQ_result_spec_string ("unit",
+                                    &pd.unit),
+      TALER_PQ_result_spec_amount_with_currency ("price",
+                                                 &pd.price),
+      TALER_PQ_result_spec_json ("taxes",
+                                 &pd.taxes),
+      GNUNET_PQ_result_spec_uint64 ("total_stock",
+                                    &pd.total_stock),
+      GNUNET_PQ_result_spec_uint64 ("total_sold",
+                                    &pd.total_sold),
+      GNUNET_PQ_result_spec_uint64 ("total_lost",
+                                    &pd.total_lost),
+      GNUNET_PQ_result_spec_string ("image",
+                                    &pd.image),
+      TALER_PQ_result_spec_json ("address",
+                                 &pd.address),
+      GNUNET_PQ_result_spec_timestamp ("next_restock",
+                                       &pd.next_restock),
+      GNUNET_PQ_result_spec_uint32 ("minimum_age",
+                                    &pd.minimum_age),
+      GNUNET_PQ_result_spec_array_uint64 (pg->conn,
+                                          "categories",
+                                          &num_categories,
+                                          &categories),
+      GNUNET_PQ_result_spec_end
+    };
+
+    if (GNUNET_OK !=
+        GNUNET_PQ_extract_result (result,
+                                  rs,
+                                  i))
+    {
+      GNUNET_break (0);
+      plc->extract_failed = true;
+      return;
+    }
+    plc->cb (plc->cb_cls,
+             product_serial,
+             product_id,
+             &pd,
+             num_categories,
+             categories);
+    GNUNET_PQ_cleanup_result (rs);
+  }
+}
+
+
+enum GNUNET_DB_QueryStatus
+TMH_PG_lookup_all_products (void *cls,
+                            const char *instance_id,
+                            TALER_MERCHANTDB_ProductCallback cb,
+                            void *cb_cls)
+{
+  struct PostgresClosure *pg = cls;
+  struct LookupProductsContext plc = {
+    .cb = cb,
+    .cb_cls = cb_cls,
+    .pg = pg,
+    /* Can be overwritten by the lookup_products_cb */
+    .extract_failed = false,
+  };
+  struct GNUNET_PQ_QueryParam params[] = {
+    GNUNET_PQ_query_param_string (instance_id),
+    GNUNET_PQ_query_param_end
+  };
+  enum GNUNET_DB_QueryStatus qs;
+
+  check_connection (pg);
+  PREPARE (pg,
+           "lookup_all_products",
+           "SELECT"
+           " description"
+           ",description_i18n"
+           ",unit"
+           ",price"
+           ",taxes"
+           ",total_stock"
+           ",total_sold"
+           ",total_lost"
+           ",image"
+           ",merchant_inventory.address"
+           ",next_restock"
+           ",minimum_age"
+           ",product_id"
+           ",product_serial"
+           " FROM merchant_inventory"
+           " JOIN merchant_instances"
+           "   USING (merchant_serial)"
+           ",LATERAL ("
+           "   SELECT ARRAY ("
+           "     SELECT mpc.category_serial"
+           "       FROM merchant_product_categories mpc"
+           "      WHERE mpc.product_serial = mi.product_serial"
+           "   ) AS category_array"
+           " ) t"
+           " WHERE merchant_instances.merchant_id=$1");
+  qs = GNUNET_PQ_eval_prepared_multi_select (
+    pg->conn,
+    "lookup_all_products",
+    params,
+    &lookup_products_cb,
+    &plc);
+  /* If there was an error inside lookup_products_cb, return a hard error. */
+  if (plc.extract_failed)
+    return GNUNET_DB_STATUS_HARD_ERROR;
+  return qs;
+}
diff --git a/src/backenddb/pg_lookup_all_products.h b/src/backenddb/pg_lookup_all_products.h
new file mode 100644
index 00000000..390fa60d
--- /dev/null
+++ b/src/backenddb/pg_lookup_all_products.h
@@ -0,0 +1,46 @@
+/*
+   This file is part of TALER
+   Copyright (C) 2024 Taler Systems SA
+
+   TALER is free software; you can redistribute it and/or modify it under the
+   terms of the GNU General Public License as published by the Free Software
+   Foundation; either version 3, or (at your option) any later version.
+
+   TALER is distributed in the hope that it will be useful, but WITHOUT ANY
+   WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR
+   A PARTICULAR PURPOSE.  See the GNU General Public License for more details.
+
+   You should have received a copy of the GNU General Public License along with
+   TALER; see the file COPYING.  If not, see <http://www.gnu.org/licenses/>
+ */
+/**
+ * @file backenddb/pg_lookup_all_products.h
+ * @brief implementation of the lookup_all_products function for Postgres
+ * @author Christian Grothoff
+ */
+#ifndef PG_LOOKUP_ALL_PRODUCTS_H
+#define PG_LOOKUP_ALL_PRODUCTS_H
+
+#include <taler/taler_util.h>
+#include <taler/taler_json_lib.h>
+#include "taler_merchantdb_plugin.h"
+
+/**
+ * Lookup all of the products the given instance has configured.
+ *
+ * @param cls closure
+ * @param instance_id instance to lookup products for
+ * @param offset transfer_serial number of the transfer we want to offset from
+ * @param limit number of entries to return, negative for descending,
+ *                positive for ascending
+ * @param cb function to call on all products found
+ * @param cb_cls closure for @a cb
+ * @return database result code
+ */
+enum GNUNET_DB_QueryStatus
+TMH_PG_lookup_all_products (void *cls,
+                            const char *instance_id,
+                            TALER_MERCHANTDB_ProductCallback cb,
+                            void *cb_cls);
+
+#endif
diff --git a/src/backenddb/pg_lookup_categories.c b/src/backenddb/pg_lookup_categories.c
new file mode 100644
index 00000000..9aea5477
--- /dev/null
+++ b/src/backenddb/pg_lookup_categories.c
@@ -0,0 +1,148 @@
+/*
+   This file is part of TALER
+   Copyright (C) 2024 Taler Systems SA
+
+   TALER is free software; you can redistribute it and/or modify it under the
+   terms of the GNU General Public License as published by the Free Software
+   Foundation; either version 3, or (at your option) any later version.
+
+   TALER is distributed in the hope that it will be useful, but WITHOUT ANY
+   WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR
+   A PARTICULAR PURPOSE.  See the GNU General Public License for more details.
+
+   You should have received a copy of the GNU General Public License along with
+   TALER; see the file COPYING.  If not, see <http://www.gnu.org/licenses/>
+ */
+/**
+ * @file backenddb/pg_lookup_categories.c
+ * @brief Implementation of the lookup_categories function for Postgres
+ * @author Christian Grothoff
+ */
+#include "platform.h"
+#include <taler/taler_error_codes.h>
+#include <taler/taler_dbevents.h>
+#include <taler/taler_pq_lib.h>
+#include "pg_lookup_categories.h"
+#include "pg_helper.h"
+
+
+/**
+ * Context used for TMH_PG_lookup_categories().
+ */
+struct LookupCategoryContext
+{
+  /**
+   * Function to call with the results.
+   */
+  TALER_MERCHANTDB_CategoriesCallback cb;
+
+  /**
+   * Closure for @a cb.
+   */
+  void *cb_cls;
+
+  /**
+   * Did database result extraction fail?
+   */
+  bool extract_failed;
+};
+
+
+/**
+ * Function to be called with the results of a SELECT statement
+ * that has returned @a num_results results about otp_device.
+ *
+ * @param[in,out] cls of type `struct LookupCategoryContext *`
+ * @param result the postgres result
+ * @param num_results the number of results in @a result
+ */
+static void
+lookup_categories_cb (void *cls,
+                      PGresult *result,
+                      unsigned int num_results)
+{
+  struct LookupCategoryContext *tlc = cls;
+
+  for (unsigned int i = 0; i < num_results; i++)
+  {
+    uint64_t category_id;
+    char *category_name;
+    json_t *category_name_i18n;
+    uint64_t product_count;
+    struct GNUNET_PQ_ResultSpec rs[] = {
+      GNUNET_PQ_result_spec_uint64 ("category_serial",
+                                    &category_id),
+      GNUNET_PQ_result_spec_string ("category_name",
+                                    &category_name),
+      TALER_PQ_result_spec_json ("category_name_i18n",
+                                 &category_name_i18n),
+      GNUNET_PQ_result_spec_uint64 ("product_count",
+                                    &product_count),
+      GNUNET_PQ_result_spec_end
+    };
+
+    if (GNUNET_OK !=
+        GNUNET_PQ_extract_result (result,
+                                  rs,
+                                  i))
+    {
+      GNUNET_break (0);
+      tlc->extract_failed = true;
+      return;
+    }
+    tlc->cb (tlc->cb_cls,
+             category_id,
+             category_name,
+             category_name_i18n,
+             product_count);
+    GNUNET_PQ_cleanup_result (rs);
+  }
+}
+
+
+enum GNUNET_DB_QueryStatus
+TMH_PG_lookup_categories (void *cls,
+                          const char *instance_id,
+                          TALER_MERCHANTDB_CategoriesCallback cb,
+                          void *cb_cls)
+{
+
+  struct PostgresClosure *pg = cls;
+  struct LookupCategoryContext tlc = {
+    .cb = cb,
+    .cb_cls = cb_cls,
+    /* Can be overwritten by the lookup_categories_cb */
+    .extract_failed = false,
+  };
+  struct GNUNET_PQ_QueryParam params[] = {
+    GNUNET_PQ_query_param_string (instance_id),
+    GNUNET_PQ_query_param_end
+  };
+  enum GNUNET_DB_QueryStatus qs;
+
+  check_connection (pg);
+  PREPARE (pg,
+           "lookup_categories",
+           "SELECT"
+           " mc.category_serial"
+           ",mc.category_name"
+           ",mc.category_name_i18n"
+           ",COALESCE(COUNT(mpc.product_serial),0)"
+           "   AS product_count"
+           " FROM merchant_categories mc"
+           " JOIN merchant_product_categories mpc"
+           " JOIN merchant_instances mi"
+           "   USING (merchant_serial)"
+           " WHERE mi.merchant_id=$1"
+           " GROUP BY mc.category_serial"
+           " ORDER BY mc.category_serial;");
+  qs = GNUNET_PQ_eval_prepared_multi_select (pg->conn,
+                                             "lookup_categories",
+                                             params,
+                                             &lookup_categories_cb,
+                                             &tlc);
+  /* If there was an error inside lookup_categories_cb, return a hard error. */
+  if (tlc.extract_failed)
+    return GNUNET_DB_STATUS_HARD_ERROR;
+  return qs;
+}
diff --git a/src/backenddb/pg_lookup_categories.h b/src/backenddb/pg_lookup_categories.h
new file mode 100644
index 00000000..500295c0
--- /dev/null
+++ b/src/backenddb/pg_lookup_categories.h
@@ -0,0 +1,43 @@
+/*
+   This file is part of TALER
+   Copyright (C) 2024 Taler Systems SA
+
+   TALER is free software; you can redistribute it and/or modify it under the
+   terms of the GNU General Public License as published by the Free Software
+   Foundation; either version 3, or (at your option) any later version.
+
+   TALER is distributed in the hope that it will be useful, but WITHOUT ANY
+   WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR
+   A PARTICULAR PURPOSE.  See the GNU General Public License for more details.
+
+   You should have received a copy of the GNU General Public License along with
+   TALER; see the file COPYING.  If not, see <http://www.gnu.org/licenses/>
+ */
+/**
+ * @file backenddb/pg_lookup_categories.h
+ * @brief implementation of the lookup_categories function for Postgres
+ * @author Christian Grothoff
+ */
+#ifndef PG_LOOKUP_CATEGORIES_H
+#define PG_LOOKUP_CATEGORIES_H
+
+#include <taler/taler_util.h>
+#include <taler/taler_json_lib.h>
+#include "taler_merchantdb_plugin.h"
+
+/**
+ * Lookup all of the product categories the given instance has configured.
+ *
+ * @param cls closure
+ * @param instance_id instance to lookup OTP devices for
+ * @param cb function to call on all categories found
+ * @param cb_cls closure for @a cb
+ * @return database result code
+ */
+enum GNUNET_DB_QueryStatus
+TMH_PG_lookup_categories (void *cls,
+                          const char *instance_id,
+                          TALER_MERCHANTDB_CategoriesCallback cb,
+                          void *cb_cls);
+
+#endif
diff --git a/src/backenddb/pg_lookup_instances.c b/src/backenddb/pg_lookup_instances.c
index 323b1957..f4f820ac 100644
--- a/src/backenddb/pg_lookup_instances.c
+++ b/src/backenddb/pg_lookup_instances.c
@@ -173,7 +173,6 @@ lookup_instances_cb (void *cls,
   {
     bool no_auth;
     bool no_salt;
-    uint32_t ut32;
     struct GNUNET_PQ_ResultSpec rs[] = {
       GNUNET_PQ_result_spec_uint64 ("merchant_serial",
                                     &lic->instance_serial),
@@ -191,8 +190,6 @@ lookup_instances_cb (void *cls,
                                     &lic->is.id),
       GNUNET_PQ_result_spec_string ("merchant_name",
                                     &lic->is.name),
-      GNUNET_PQ_result_spec_uint32 ("user_type",
-                                    &ut32),
       TALER_PQ_result_spec_json ("address",
                                  &lic->is.address),
       TALER_PQ_result_spec_json ("jurisdiction",
@@ -200,7 +197,8 @@ lookup_instances_cb (void *cls,
       GNUNET_PQ_result_spec_bool ("use_stefan",
                                   &lic->is.use_stefan),
       GNUNET_PQ_result_spec_relative_time ("default_wire_transfer_delay",
-                                           &lic->is.default_wire_transfer_delay),
+                                           &lic->is.default_wire_transfer_delay)
+      ,
       GNUNET_PQ_result_spec_relative_time ("default_pay_delay",
                                            &lic->is.default_pay_delay),
       GNUNET_PQ_result_spec_allow_null (
@@ -233,7 +231,6 @@ lookup_instances_cb (void *cls,
       lic->qs = GNUNET_DB_STATUS_HARD_ERROR;
       return;
     }
-    lic->is.ut = (enum TALER_KYCLOGIC_KycUserType) ut32;
     call_cb (lic);
     GNUNET_PQ_cleanup_result (rs);
     if (0 > lic->qs)
@@ -270,7 +267,6 @@ TMH_PG_lookup_instances (void *cls,
            ",auth_salt"
            ",merchant_id"
            ",merchant_name"
-           ",user_type"
            ",address"
            ",jurisdiction"
            ",use_stefan"
diff --git a/src/backenddb/pg_lookup_product.c b/src/backenddb/pg_lookup_product.c
index 65a3c0e5..2948e6ca 100644
--- a/src/backenddb/pg_lookup_product.c
+++ b/src/backenddb/pg_lookup_product.c
@@ -29,7 +29,9 @@ enum GNUNET_DB_QueryStatus
 TMH_PG_lookup_product (void *cls,
                        const char *instance_id,
                        const char *product_id,
-                       struct TALER_MERCHANTDB_ProductDetails *pd)
+                       struct TALER_MERCHANTDB_ProductDetails *pd,
+                       size_t *num_categories,
+                       uint64_t **categories)
 {
   struct PostgresClosure *pg = cls;
   struct GNUNET_PQ_QueryParam params[] = {
@@ -38,6 +40,35 @@ TMH_PG_lookup_product (void *cls,
     GNUNET_PQ_query_param_end
   };
 
+  PREPARE (pg,
+           "lookup_product",
+           "SELECT"
+           " mi.description"
+           ",mi.description_i18n"
+           ",mi.unit"
+           ",mi.price"
+           ",mi.taxes"
+           ",mi.total_stock"
+           ",mi.total_sold"
+           ",mi.total_lost"
+           ",mi.image"
+           ",mi.address"
+           ",mi.next_restock"
+           ",mi.minimum_age"
+           ",t.category_array AS categories"
+           " FROM merchant_inventory mi"
+           " JOIN merchant_instances inst"
+           "   USING (merchant_serial)"
+           ",LATERAL ("
+           "   SELECT ARRAY ("
+           "     SELECT mpc.category_serial"
+           "       FROM merchant_product_categories mpc"
+           "      WHERE mpc.product_serial = mi.product_serial"
+           "   ) AS category_array"
+           " ) t"
+           " WHERE inst.merchant_id=$1"
+           "   AND mi.product_id=$2"
+           );
   if (NULL == pd)
   {
     struct GNUNET_PQ_ResultSpec rs_null[] = {
@@ -60,7 +91,7 @@ TMH_PG_lookup_product (void *cls,
       GNUNET_PQ_result_spec_string ("unit",
                                     &pd->unit),
       TALER_PQ_result_spec_amount_with_currency ("price",
-                                   &pd->price),
+                                                 &pd->price),
       TALER_PQ_result_spec_json ("taxes",
                                  &pd->taxes),
       GNUNET_PQ_result_spec_uint64 ("total_stock",
@@ -77,30 +108,14 @@ TMH_PG_lookup_product (void *cls,
                                        &pd->next_restock),
       GNUNET_PQ_result_spec_uint32 ("minimum_age",
                                     &pd->minimum_age),
+      GNUNET_PQ_result_spec_array_uint64 (pg->conn,
+                                          "categories",
+                                          num_categories,
+                                          categories),
       GNUNET_PQ_result_spec_end
     };
 
     check_connection (pg);
-    PREPARE (pg,
-             "lookup_product",
-             "SELECT"
-             " description"
-             ",description_i18n"
-             ",unit"
-             ",price"
-             ",taxes"
-             ",total_stock"
-             ",total_sold"
-             ",total_lost"
-             ",image"
-             ",merchant_inventory.address"
-             ",next_restock"
-             ",minimum_age"
-             " FROM merchant_inventory"
-             " JOIN merchant_instances"
-             "   USING (merchant_serial)"
-             " WHERE merchant_instances.merchant_id=$1"
-             "   AND merchant_inventory.product_id=$2");
     return GNUNET_PQ_eval_prepared_singleton_select (pg->conn,
                                                      "lookup_product",
                                                      params,
diff --git a/src/backenddb/pg_lookup_product.h b/src/backenddb/pg_lookup_product.h
index a6add4cb..7346cc0d 100644
--- a/src/backenddb/pg_lookup_product.h
+++ b/src/backenddb/pg_lookup_product.h
@@ -33,12 +33,17 @@
  * @param product_id product to lookup
  * @param[out] pd set to the product details on success, can be NULL
  *             (in that case we only want to check if the product exists)
+ * @param[out] num_categories set to length of @a categories array
+ * @param[out] categories set to array of categories the
+ *   product is in, caller must free() it.
  * @return database result code
  */
 enum GNUNET_DB_QueryStatus
 TMH_PG_lookup_product (void *cls,
                        const char *instance_id,
                        const char *product_id,
-                       struct TALER_MERCHANTDB_ProductDetails *pd);
+                       struct TALER_MERCHANTDB_ProductDetails *pd,
+                       size_t *num_categories,
+                       uint64_t **categories);
 
 #endif
diff --git a/src/backenddb/pg_select_category.c b/src/backenddb/pg_select_category.c
new file mode 100644
index 00000000..c20d7bb7
--- /dev/null
+++ b/src/backenddb/pg_select_category.c
@@ -0,0 +1,37 @@
+/*
+   This file is part of TALER
+   Copyright (C) 2024 Taler Systems SA
+
+   TALER is free software; you can redistribute it and/or modify it under the
+   terms of the GNU General Public License as published by the Free Software
+   Foundation; either version 3, or (at your option) any later version.
+
+   TALER is distributed in the hope that it will be useful, but WITHOUT ANY
+   WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR
+   A PARTICULAR PURPOSE.  See the GNU General Public License for more details.
+
+   You should have received a copy of the GNU General Public License along with
+   TALER; see the file COPYING.  If not, see <http://www.gnu.org/licenses/>
+ */
+/**
+ * @file backenddb/pg_select_category.c
+ * @brief Implementation of the select_category function for Postgres
+ * @author Christian Grothoff
+ */
+#include "platform.h"
+#include <taler/taler_error_codes.h>
+#include <taler/taler_dbevents.h>
+#include <taler/taler_pq_lib.h>
+#include "pg_select_category.h"
+#include "pg_helper.h"
+
+
+enum GNUNET_DB_QueryStatus
+TMH_PG_select_category (void *cls,
+                        const char *instance_id,
+                        uint64_t category_id,
+                        struct TALER_MERCHANTDB_CategoryDetails *cd)
+{
+  GNUNET_break (0); // FIXME
+  return GNUNET_DB_STATUS_HARD_ERROR;
+}
diff --git a/src/backenddb/pg_select_category.h b/src/backenddb/pg_select_category.h
new file mode 100644
index 00000000..9eeb14aa
--- /dev/null
+++ b/src/backenddb/pg_select_category.h
@@ -0,0 +1,45 @@
+/*
+   This file is part of TALER
+   Copyright (C) 2024 Taler Systems SA
+
+   TALER is free software; you can redistribute it and/or modify it under the
+   terms of the GNU General Public License as published by the Free Software
+   Foundation; either version 3, or (at your option) any later version.
+
+   TALER is distributed in the hope that it will be useful, but WITHOUT ANY
+   WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR
+   A PARTICULAR PURPOSE.  See the GNU General Public License for more details.
+
+   You should have received a copy of the GNU General Public License along with
+   TALER; see the file COPYING.  If not, see <http://www.gnu.org/licenses/>
+ */
+/**
+ * @file backenddb/pg_select_category.h
+ * @brief implementation of the select_category function for Postgres
+ * @author Christian Grothoff
+ */
+#ifndef PG_SELECT_CATEGORY_H
+#define PG_SELECT_CATEGORY_H
+
+#include <taler/taler_util.h>
+#include <taler/taler_json_lib.h>
+#include "taler_merchantdb_plugin.h"
+
+
+/**
+ * Lookup details about product category.
+ *
+ * @param cls closure
+ * @param instance_id instance to lookup template for
+ * @param category_id category to update
+ * @param[out] cd set to the category details on success, can be NULL
+ *             (in that case we only want to check if the category exists)
+ * @return database result code
+ */
+enum GNUNET_DB_QueryStatus
+TMH_PG_select_category (void *cls,
+                        const char *instance_id,
+                        uint64_t category_id,
+                        struct TALER_MERCHANTDB_CategoryDetails *cd);
+
+#endif
diff --git a/src/backenddb/pg_select_category_by_name.c b/src/backenddb/pg_select_category_by_name.c
new file mode 100644
index 00000000..9c2aa784
--- /dev/null
+++ b/src/backenddb/pg_select_category_by_name.c
@@ -0,0 +1,68 @@
+/*
+   This file is part of TALER
+   Copyright (C) 2024 Taler Systems SA
+
+   TALER is free software; you can redistribute it and/or modify it under the
+   terms of the GNU General Public License as published by the Free Software
+   Foundation; either version 3, or (at your option) any later version.
+
+   TALER is distributed in the hope that it will be useful, but WITHOUT ANY
+   WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR
+   A PARTICULAR PURPOSE.  See the GNU General Public License for more details.
+
+   You should have received a copy of the GNU General Public License along with
+   TALER; see the file COPYING.  If not, see <http://www.gnu.org/licenses/>
+ */
+/**
+ * @file backenddb/pg_select_category_by_name.c
+ * @brief Implementation of the select_category_by_name function for Postgres
+ * @author Christian Grothoff
+ */
+#include "platform.h"
+#include <taler/taler_error_codes.h>
+#include <taler/taler_dbevents.h>
+#include <taler/taler_pq_lib.h>
+#include "pg_select_category_by_name.h"
+#include "pg_helper.h"
+
+
+enum GNUNET_DB_QueryStatus
+TMH_PG_select_category_by_name (void *cls,
+                                const char *instance_id,
+                                const char *category_name,
+                                json_t **name_i18n,
+                                uint64_t *category_id)
+{
+  struct PostgresClosure *pg = cls;
+  struct GNUNET_PQ_QueryParam params[] = {
+    GNUNET_PQ_query_param_string (instance_id),
+    GNUNET_PQ_query_param_string (category_name),
+    GNUNET_PQ_query_param_end
+  };
+  struct GNUNET_PQ_ResultSpec rs[] = {
+    GNUNET_PQ_result_spec_uint64 ("category_serial",
+                                  category_id),
+    TALER_PQ_result_spec_json ("category_name_i18n",
+                               name_i18n),
+    GNUNET_PQ_result_spec_end
+  };
+
+  PREPARE (pg,
+           "select_category_by_name",
+           "SELECT"
+           " category_serial"
+           ",category_name_i18n"
+           " FROM merchant_categories mc"
+           " JOIN merchant_instances mi"
+           "   USING (merchant_serial)"
+           " WHERE mi.merchant_id=$1"
+           "   AND mc.category_name=$2");
+
+
+  check_connection (pg);
+  return GNUNET_PQ_eval_prepared_singleton_select (
+    pg->conn,
+    "select_category_by_name",
+    params,
+    rs);
+}
diff --git a/src/backenddb/pg_select_category_by_name.h b/src/backenddb/pg_select_category_by_name.h
new file mode 100644
index 00000000..4f582828
--- /dev/null
+++ b/src/backenddb/pg_select_category_by_name.h
@@ -0,0 +1,46 @@
+/*
+   This file is part of TALER
+   Copyright (C) 2024 Taler Systems SA
+
+   TALER is free software; you can redistribute it and/or modify it under the
+   terms of the GNU General Public License as published by the Free Software
+   Foundation; either version 3, or (at your option) any later version.
+
+   TALER is distributed in the hope that it will be useful, but WITHOUT ANY
+   WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR
+   A PARTICULAR PURPOSE.  See the GNU General Public License for more details.
+
+   You should have received a copy of the GNU General Public License along with
+   TALER; see the file COPYING.  If not, see <http://www.gnu.org/licenses/>
+ */
+/**
+ * @file backenddb/pg_select_category_by_name.h
+ * @brief implementation of the select_category_by_name function for Postgres
+ * @author Christian Grothoff
+ */
+#ifndef PG_SELECT_CATEGORY_BY_NAME_H
+#define PG_SELECT_CATEGORY_BY_NAME_H
+
+#include <taler/taler_util.h>
+#include <taler/taler_json_lib.h>
+#include "taler_merchantdb_plugin.h"
+
+
+/**
+ * Lookup details about product category by name.
+ *
+ * @param cls closure
+ * @param instance_id instance to lookup template for
+ * @param category_name category name to look for
+ * @param[out] name_i18n category name translation
+ * @param[out] category_id category ID
+ * @return database result code
+ */
+enum GNUNET_DB_QueryStatus
+TMH_PG_select_category_by_name (void *cls,
+                                const char *instance_id,
+                                const char *category_name,
+                                json_t **name_i18n,
+                                uint64_t *category_id);
+
+#endif
diff --git a/src/backenddb/pg_update_category.c b/src/backenddb/pg_update_category.c
new file mode 100644
index 00000000..3b07a266
--- /dev/null
+++ b/src/backenddb/pg_update_category.c
@@ -0,0 +1,59 @@
+/*
+   This file is part of TALER
+   Copyright (C) 2024 Taler Systems SA
+
+   TALER is free software; you can redistribute it and/or modify it under the
+   terms of the GNU General Public License as published by the Free Software
+   Foundation; either version 3, or (at your option) any later version.
+
+   TALER is distributed in the hope that it will be useful, but WITHOUT ANY
+   WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR
+   A PARTICULAR PURPOSE.  See the GNU General Public License for more details.
+
+   You should have received a copy of the GNU General Public License along with
+   TALER; see the file COPYING.  If not, see <http://www.gnu.org/licenses/>
+ */
+/**
+ * @file backenddb/pg_update_category.c
+ * @brief Implementation of the update_category function for Postgres
+ * @author Christian Grothoff
+ */
+#include "platform.h"
+#include <taler/taler_error_codes.h>
+#include <taler/taler_dbevents.h>
+#include <taler/taler_pq_lib.h>
+#include "pg_update_category.h"
+#include "pg_helper.h"
+
+
+enum GNUNET_DB_QueryStatus
+TMH_PG_update_category (void *cls,
+                        const char *instance_id,
+                        uint64_t category_id,
+                        const char *category_name,
+                        const json_t *category_name_i18n)
+{
+  struct PostgresClosure *pg = cls;
+  struct GNUNET_PQ_QueryParam params[] = {
+    GNUNET_PQ_query_param_string (instance_id),
+    GNUNET_PQ_query_param_uint64 (&category_id),
+    GNUNET_PQ_query_param_string (category_name),
+    TALER_PQ_query_param_json (category_name_i18n),
+    GNUNET_PQ_query_param_end
+  };
+
+  check_connection (pg);
+  PREPARE (pg,
+           "update_category",
+           "UPDATE merchant_categories SET"
+           " category_name=$3"
+           ",category_name_i18n=$4"
+           " WHERE merchant_serial="
+           "   (SELECT merchant_serial"
+           "      FROM merchant_instances"
+           "      WHERE merchant_id=$1)"
+           "   AND category_serial=$2");
+  return GNUNET_PQ_eval_prepared_non_select (pg->conn,
+                                             "update_category",
+                                             params);
+}
diff --git a/src/backenddb/pg_update_category.h b/src/backenddb/pg_update_category.h
new file mode 100644
index 00000000..616a714a
--- /dev/null
+++ b/src/backenddb/pg_update_category.h
@@ -0,0 +1,47 @@
+/*
+   This file is part of TALER
+   Copyright (C) 2024 Taler Systems SA
+
+   TALER is free software; you can redistribute it and/or modify it under the
+   terms of the GNU General Public License as published by the Free Software
+   Foundation; either version 3, or (at your option) any later version.
+
+   TALER is distributed in the hope that it will be useful, but WITHOUT ANY
+   WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR
+   A PARTICULAR PURPOSE.  See the GNU General Public License for more details.
+
+   You should have received a copy of the GNU General Public License along with
+   TALER; see the file COPYING.  If not, see <http://www.gnu.org/licenses/>
+ */
+/**
+ * @file backenddb/pg_update_category.h
+ * @brief implementation of the update_category function for Postgres
+ * @author Christian Grothoff
+ */
+#ifndef PG_UPDATE_CATEGORY_H
+#define PG_UPDATE_CATEGORY_H
+
+#include <taler/taler_util.h>
+#include <taler/taler_json_lib.h>
+#include "taler_merchantdb_plugin.h"
+
+
+/**
+ * Update descriptions of a product category.
+ *
+ * @param cls closure
+ * @param instance_id instance to update OTP device for
+ * @param category_id category to update
+ * @param category_name name of the category
+ * @param category_name_i18n translations of the category name
+ * @return database result code, #GNUNET_DB_STATUS_SUCCESS_NO_RESULTS if the template
+ *         does not yet exist.
+ */
+enum GNUNET_DB_QueryStatus
+TMH_PG_update_category (void *cls,
+                        const char *instance_id,
+                        uint64_t category_id,
+                        const char *category_name,
+                        const json_t *category_name_i18n);
+
+#endif
diff --git a/src/backenddb/pg_update_instance.c b/src/backenddb/pg_update_instance.c
index 228e2031..91026638 100644
--- a/src/backenddb/pg_update_instance.c
+++ b/src/backenddb/pg_update_instance.c
@@ -32,7 +32,6 @@ TMH_PG_update_instance (void *cls,
                         const struct TALER_MERCHANTDB_InstanceSettings *is)
 {
   struct PostgresClosure *pg = cls;
-  uint32_t ut32 = (uint32_t) is->ut;
   struct GNUNET_PQ_QueryParam params[] = {
     GNUNET_PQ_query_param_string (is->id),
     GNUNET_PQ_query_param_string (is->name),
@@ -52,7 +51,6 @@ TMH_PG_update_instance (void *cls,
     (NULL == is->logo)
     ? GNUNET_PQ_query_param_null ()
     : GNUNET_PQ_query_param_string (is->logo),
-    GNUNET_PQ_query_param_uint32 (&ut32),
     GNUNET_PQ_query_param_end
   };
 
@@ -69,7 +67,6 @@ TMH_PG_update_instance (void *cls,
            ",website=$8"
            ",email=$9"
            ",logo=$10"
-           ",user_type=$11"
            " WHERE merchant_id=$1");
   return GNUNET_PQ_eval_prepared_non_select (pg->conn,
                                              "update_instance",
diff --git a/src/backenddb/pg_update_otp.c b/src/backenddb/pg_update_otp.c
index bdcb9624..218ae74e 100644
--- a/src/backenddb/pg_update_otp.c
+++ b/src/backenddb/pg_update_otp.c
@@ -26,17 +26,6 @@
 #include "pg_helper.h"
 
 
-/**
- * Update details about a particular OTP device.
- *
- * @param cls closure
- * @param instance_id instance to update OTP device for
- * @param otp_id OTP device to update
- * @param td update to the OTP device details on success, can be NULL
- *             (in that case we only want to check if the template exists)
- * @return database result code, #GNUNET_DB_STATUS_SUCCESS_NO_RESULTS if the template
- *         does not yet exist.
- */
 enum GNUNET_DB_QueryStatus
 TMH_PG_update_otp (void *cls,
                    const char *instance_id,
@@ -52,7 +41,7 @@ TMH_PG_update_otp (void *cls,
     GNUNET_PQ_query_param_uint32 (&pos32),
     GNUNET_PQ_query_param_uint64 (&td->otp_ctr),
     (NULL == td->otp_key)
-    ? GNUNET_PQ_query_param_null()
+    ? GNUNET_PQ_query_param_null ()
     : GNUNET_PQ_query_param_string (td->otp_key),
     GNUNET_PQ_query_param_end
   };
@@ -74,5 +63,3 @@ TMH_PG_update_otp (void *cls,
                                              "update_otp",
                                              params);
 }
-
-
diff --git a/src/backenddb/pg_update_product.c b/src/backenddb/pg_update_product.c
index cd7c1857..d7b63b82 100644
--- a/src/backenddb/pg_update_product.c
+++ b/src/backenddb/pg_update_product.c
@@ -1,6 +1,6 @@
 /*
    This file is part of TALER
-   Copyright (C) 2022 Taler Systems SA
+   Copyright (C) 2022, 2024 Taler Systems SA
 
    TALER is free software; you can redistribute it and/or modify it under the
    terms of the GNU General Public License as published by the Free Software
@@ -26,11 +26,20 @@
 #include "pg_update_product.h"
 #include "pg_helper.h"
 
+
 enum GNUNET_DB_QueryStatus
 TMH_PG_update_product (void *cls,
                        const char *instance_id,
                        const char *product_id,
-                       const struct TALER_MERCHANTDB_ProductDetails *pd)
+                       const struct TALER_MERCHANTDB_ProductDetails *pd,
+                       size_t num_cats,
+                       const uint64_t *cats,
+                       bool *no_instance,
+                       ssize_t *no_cat,
+                       bool *no_product,
+                       bool *lost_reduced,
+                       bool *sold_reduced,
+                       bool *stocked_reduced)
 {
   struct PostgresClosure *pg = cls;
   struct GNUNET_PQ_QueryParam params[] = {
@@ -42,14 +51,37 @@ TMH_PG_update_product (void *cls,
     GNUNET_PQ_query_param_string (pd->image), /* $6 */
     TALER_PQ_query_param_json (pd->taxes),
     TALER_PQ_query_param_amount_with_currency (pg->conn,
-                                 &pd->price),       /* $8 */
+                                               &pd->price), /* $8 */
     GNUNET_PQ_query_param_uint64 (&pd->total_stock),  /* $9 */
     GNUNET_PQ_query_param_uint64 (&pd->total_lost),
     TALER_PQ_query_param_json (pd->address),
     GNUNET_PQ_query_param_timestamp (&pd->next_restock),
     GNUNET_PQ_query_param_uint32 (&pd->minimum_age),
+    GNUNET_PQ_query_param_array_uint64 (num_cats,
+                                        cats,
+                                        pg->conn),
     GNUNET_PQ_query_param_end
   };
+  uint64_t ncat;
+  bool cats_found = true;
+  struct GNUNET_PQ_ResultSpec rs[] = {
+    GNUNET_PQ_result_spec_bool ("no_instance",
+                                no_instance),
+    GNUNET_PQ_result_spec_bool ("no_product",
+                                no_product),
+    GNUNET_PQ_result_spec_bool ("lost_reduced",
+                                lost_reduced),
+    GNUNET_PQ_result_spec_bool ("sold_reduced",
+                                sold_reduced),
+    GNUNET_PQ_result_spec_bool ("stocked_reduced",
+                                stocked_reduced),
+    GNUNET_PQ_result_spec_allow_null (
+      GNUNET_PQ_result_spec_uint64 ("no_cat",
+                                    &ncat),
+      &cats_found),
+    GNUNET_PQ_result_spec_end
+  };
+  enum GNUNET_DB_QueryStatus qs;
 
   if ( (pd->total_stock < pd->total_lost + pd->total_sold) ||
        (pd->total_lost < pd->total_lost
@@ -61,26 +93,20 @@ TMH_PG_update_product (void *cls,
   check_connection (pg);
   PREPARE (pg,
            "update_product",
-           "UPDATE merchant_inventory SET"
-           " description=$3"
-           ",description_i18n=$4"
-           ",unit=$5"
-           ",image=$6"
-           ",taxes=$7"
-           ",price=$8"
-           ",total_stock=$9"
-           ",total_lost=$10"
-           ",address=$11"
-           ",next_restock=$12"
-           ",minimum_age=$13"
-           " WHERE merchant_serial="
-           "   (SELECT merchant_serial"
-           "      FROM merchant_instances"
-           "      WHERE merchant_id=$1)"
-           "   AND product_id=$2"
-           "   AND total_stock <= $9"
-           "   AND total_lost <= $10");
-  return GNUNET_PQ_eval_prepared_non_select (pg->conn,
-                                             "update_product",
-                                             params);
+           "SELECT"
+           " out_lost_reduced AS lost_reduced"
+           ",out_sold_reduced AS sold_reduced"
+           ",out_stocked_reduced AS stocked_reduced"
+           ",out_no_product AS no_product"
+           ",out_no_cat AS no_cat"
+           ",out_no_instance AS no_instance"
+           " FROM merchant_do_update_product"
+           "($1, $2, $3, $4, $5, $6, $7, $8, $9, $10, $11, $12, $13, $14);");
+  qs = GNUNET_PQ_eval_prepared_singleton_select (pg->conn,
+                                                 "update_product",
+                                                 params,
+                                                 rs);
+  GNUNET_PQ_cleanup_query_params_closures (params);
+  *no_cat = (cats_found) ? -1 : (ssize_t) ncat;
+  return qs;
 }
diff --git a/src/backenddb/pg_update_product.h b/src/backenddb/pg_update_product.h
index 3ad280ef..ffba1073 100644
--- a/src/backenddb/pg_update_product.h
+++ b/src/backenddb/pg_update_product.h
@@ -28,26 +28,40 @@
 /**
  * Update details about a particular product. Note that the
  * transaction must enforce that the sold/stocked/lost counters
- * are not reduced (i.e. by expanding the WHERE clause on the existing
- * values).
+ * are not reduced.
  *
  * @param cls closure
  * @param instance_id instance to lookup products for
  * @param product_id product to lookup
+ * @param num_cats length of @a cats array
+ * @param cats number of categories the product is in
+ * @param[out] no_instance the update failed as the instance is unknown
+ * @param[out] no_cat set to -1 on success, otherwise the update failed and this is set
+ *                to the index of a category in @a cats that is unknown
+ * @param[out] no_product the @a product_id is unknown
+ * @param[out] lost_reduced the update failed as the counter of units lost would have been lowered
+ * @param[out] sold_reduced the update failed as the counter of units sold would have been lowered
+ * @param[out] stocked_reduced the update failed as the counter of units stocked would have been lowered
  * @param[out] pd set to the product details on success, can be NULL
  *             (in that case we only want to check if the product exists)
  *             total_sold in @a pd is ignored, total_lost must not
  *             exceed total_stock minus the existing total_sold;
  *             total_sold and total_stock must be larger or equal to
  *             the existing value;
- * @return database result code, #GNUNET_DB_STATUS_SUCCESS_NO_RESULTS if the
- *         non-decreasing constraints are not met *or* if the product
- *         does not yet exist.
+ * @return database result code
  */
 enum GNUNET_DB_QueryStatus
 TMH_PG_update_product (void *cls,
                        const char *instance_id,
                        const char *product_id,
-                       const struct TALER_MERCHANTDB_ProductDetails *pd);
+                       const struct TALER_MERCHANTDB_ProductDetails *pd,
+                       size_t num_cats,
+                       const uint64_t *cats,
+                       bool *no_instance,
+                       ssize_t *no_cat,
+                       bool *no_product,
+                       bool *lost_reduced,
+                       bool *sold_reduced,
+                       bool *stocked_reduced);
 
 #endif
diff --git a/src/backenddb/pg_update_product.sql b/src/backenddb/pg_update_product.sql
new file mode 100644
index 00000000..6b5a416b
--- /dev/null
+++ b/src/backenddb/pg_update_product.sql
@@ -0,0 +1,139 @@
+--
+-- This file is part of TALER
+-- Copyright (C) 2024 Taler Systems SA
+--
+-- TALER is free software; you can redistribute it and/or modify it under the
+-- terms of the GNU General Public License as published by the Free Software
+-- Foundation; either version 3, or (at your option) any later version.
+--
+-- TALER is distributed in the hope that it will be useful, but WITHOUT ANY
+-- WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR
+-- A PARTICULAR PURPOSE.  See the GNU General Public License for more details.
+--
+-- You should have received a copy of the GNU General Public License along with
+-- TALER; see the file COPYING.  If not, see <http://www.gnu.org/licenses/>
+--
+
+
+CREATE OR REPLACE FUNCTION merchant_do_update_product (
+  IN in_instance_id TEXT,
+  IN in_product_id TEXT,
+  IN in_description TEXT,
+  IN in_description_i18n BYTEA,
+  IN in_unit TEXT,
+  IN in_image TEXT,
+  IN in_taxes BYTEA,
+  IN in_price taler_amount_currency,
+  IN in_total_stock INT8,
+  IN in_total_lost INT8,
+  IN in_address BYTEA,
+  IN in_next_restock INT8,
+  IN in_minimum_age INT4,
+  IN ina_categories INT8[],
+  OUT out_no_instance BOOL,
+  OUT out_no_product BOOL,
+  OUT out_lost_reduced BOOL,
+  OUT out_sold_reduced BOOL,
+  OUT out_stocked_reduced BOOL,
+  OUT out_no_cat INT8)
+LANGUAGE plpgsql
+AS $$
+DECLARE
+  my_merchant_id INT8;
+  my_product_serial INT8;
+  i INT8;
+  ini_cat INT8;
+  rec RECORD;
+BEGIN
+
+out_no_instance=FALSE;
+out_no_product=FALSE;
+out_lost_reduced=FALSE;
+out_sold_reduced=FALSE; -- We currently don't allow updating 'sold', hence always FALSE
+out_stocked_reduced=FALSE;
+out_no_cat=NULL;
+
+-- Which instance are we using?
+SELECT merchant_serial
+  INTO my_merchant_id
+  FROM merchant_instances
+ WHERE merchant_id=in_instance_id;
+
+IF NOT FOUND
+THEN
+  out_no_instance=TRUE;
+  RETURN;
+END IF;
+
+-- Check existing entry satisfies constraints
+SELECT total_stock
+      ,total_lost
+      ,product_serial
+  INTO rec
+  FROM merchant_inventory
+ WHERE merchant_serial=my_merchant_id
+   AND product_id=in_product_id;
+
+IF NOT FOUND
+THEN
+  out_no_product=TRUE;
+  RETURN;
+END IF;
+
+my_product_serial = rec.product_serial;
+
+IF rec.total_stock > in_total_stock
+THEN
+  out_stocked_reduced=TRUE;
+  RETURN;
+END IF;
+
+IF rec.total_lost > in_total_lost
+THEN
+  out_lost_reduced=TRUE;
+  RETURN;
+END IF;
+
+-- Remove old categories
+DELETE FROM merchant_product_categories
+  WHERE product_serial=my_product_serial;
+
+-- Add new categories
+FOR i IN 1..COALESCE(array_length(ina_categories,1),0)
+LOOP
+  ini_cat=ina_categories[i];
+
+  INSERT INTO merchant_product_categories
+   (product_serial
+   ,category_serial)
+  VALUES
+   (my_product_serial
+   ,ini_cat)
+  ON CONFLICT DO NOTHING;
+
+  IF NOT FOUND
+  THEN
+    out_no_cat=i;
+    RETURN;
+  END IF;
+END LOOP;
+
+UPDATE merchant_inventory SET
+   description=in_description
+  ,description_i18n=in_description_i18n
+  ,unit=in_unit
+  ,image=in_image
+  ,taxes=in_taxes
+  ,price=in_price
+  ,total_stock=in_total_stock
+  ,total_lost=in_total_lost
+  ,address=in_address
+  ,next_restock=in_next_restock
+  ,minimum_age=in_minimum_age
+ WHERE merchant_serial=my_merchant_id
+   AND product_serial=my_product_serial; -- could also match on product_id
+
+ASSERT FOUND,'SELECTED it earlier, should UPDATE it now';
+
+-- Success!
+END $$;
diff --git a/src/backenddb/plugin_merchantdb_postgres.c b/src/backenddb/plugin_merchantdb_postgres.c
index a886acaf..2f499994 100644
--- a/src/backenddb/plugin_merchantdb_postgres.c
+++ b/src/backenddb/plugin_merchantdb_postgres.c
@@ -44,6 +44,11 @@
 #include "pg_lookup_instances.h"
 #include "pg_lookup_transfers.h"
 #include "pg_lookup_pending_deposits.h"
+#include "pg_lookup_categories.h"
+#include "pg_select_category.h"
+#include "pg_update_category.h"
+#include "pg_insert_category.h"
+#include "pg_delete_category.h"
 #include "pg_update_wirewatch_progress.h"
 #include "pg_select_wirewatch_accounts.h"
 #include "pg_select_open_transfers.h"
@@ -57,12 +62,14 @@
 #include "pg_account_kyc_set_status.h"
 #include "pg_account_kyc_get_status.h"
 #include "pg_delete_instance_private_key.h"
+#include "pg_select_category_by_name.h"
 #include "pg_purge_instance.h"
 #include "pg_update_instance.h"
 #include "pg_update_instance_auth.h"
 #include "pg_inactivate_account.h"
 #include "pg_activate_account.h"
 #include "pg_lookup_products.h"
+#include "pg_lookup_all_products.h"
 #include "pg_lookup_product.h"
 #include "pg_delete_product.h"
 #include "pg_insert_product.h"
@@ -410,6 +417,8 @@ libtaler_plugin_merchantdb_postgres_init (void *cls)
     = &TMH_PG_update_transfer_status;
   plugin->lookup_products
     = &TMH_PG_lookup_products;
+  plugin->lookup_all_products
+    = &TMH_PG_lookup_all_products;
   plugin->lookup_product
     = &TMH_PG_lookup_product;
   plugin->delete_product
@@ -564,6 +573,18 @@ libtaler_plugin_merchantdb_postgres_init (void *cls)
     = &TMH_PG_insert_pending_webhook;
   plugin->update_pending_webhook
     = &TMH_PG_update_pending_webhook;
+  plugin->lookup_categories
+    = &TMH_PG_lookup_categories;
+  plugin->select_category_by_name
+    = &TMH_PG_select_category_by_name;
+  plugin->select_category
+    = &TMH_PG_select_category;
+  plugin->update_category
+    = &TMH_PG_update_category;
+  plugin->insert_category
+    = &TMH_PG_insert_category;
+  plugin->delete_category
+    = &TMH_PG_delete_category;
   plugin->delete_exchange_accounts
     = &TMH_PG_delete_exchange_accounts;
   plugin->select_accounts_by_exchange
diff --git a/src/backenddb/procedures.sql.in b/src/backenddb/procedures.sql.in
index 3ebf8b8b..9afa246b 100644
--- a/src/backenddb/procedures.sql.in
+++ b/src/backenddb/procedures.sql.in
@@ -19,6 +19,8 @@ BEGIN;
 SET search_path TO merchant;
 
 #include "pg_insert_deposit_to_transfer.sql"
+#include "pg_insert_product.sql"
 #include "pg_insert_transfer_details.sql"
+#include "pg_update_product.sql"
 
 COMMIT;
diff --git a/src/backenddb/test_merchantdb.c b/src/backenddb/test_merchantdb.c
index f113b01f..3591a133 100644
--- a/src/backenddb/test_merchantdb.c
+++ b/src/backenddb/test_merchantdb.c
@@ -797,20 +797,48 @@ check_products_equal (const struct TALER_MERCHANTDB_ProductDetails *a,
  *
  * @param instance the instance to insert the product for.
  * @param product the product data to insert.
+ * @param num_cats length of the @a cats array
+ * @param cats array of categories for the product
  * @param expected_result the result we expect the db to return.
+ * @param expect_conflict expected conflict status
+ * @param expect_no_instance expected instance missing status
+ * @param expected_no_cat expected category missing index
  * @return 0 when successful, 1 otherwise.
  */
 static int
 test_insert_product (const struct InstanceData *instance,
                      const struct ProductData *product,
-                     enum GNUNET_DB_QueryStatus expected_result)
+                     unsigned int num_cats,
+                     const uint64_t *cats,
+                     enum GNUNET_DB_QueryStatus expected_result,
+                     bool expect_conflict,
+                     bool expect_no_instance,
+                     ssize_t expected_no_cat)
 {
+  bool conflict;
+  bool no_instance;
+  ssize_t no_cat;
+
   TEST_COND_RET_ON_FAIL (expected_result ==
                          plugin->insert_product (plugin->cls,
                                                  instance->instance.id,
                                                  product->id,
-                                                 &product->product),
+                                                 &product->product,
+                                                 num_cats,
+                                                 cats,
+                                                 &no_instance,
+                                                 &conflict,
+                                                 &no_cat),
                          "Insert product failed\n");
+  if (expected_result > 0)
+  {
+    TEST_COND_RET_ON_FAIL (no_instance == expect_no_instance,
+                           "No instance wrong");
+    TEST_COND_RET_ON_FAIL (conflict == expect_conflict,
+                           "Conflict wrong");
+    TEST_COND_RET_ON_FAIL (no_cat == expected_no_cat,
+                           "Wrong category missing returned");
+  }
   return 0;
 }
 
@@ -826,14 +854,54 @@ test_insert_product (const struct InstanceData *instance,
 static int
 test_update_product (const struct InstanceData *instance,
                      const struct ProductData *product,
-                     enum GNUNET_DB_QueryStatus expected_result)
-{
-  TEST_COND_RET_ON_FAIL (expected_result ==
-                         plugin->update_product (plugin->cls,
-                                                 instance->instance.id,
-                                                 product->id,
-                                                 &product->product),
-                         "Update product failed\n");
+                     unsigned int num_cats,
+                     const uint64_t *cats,
+                     enum GNUNET_DB_QueryStatus expected_result,
+                     bool expect_no_instance,
+                     bool expect_no_product,
+                     bool expect_lost_reduced,
+                     bool expect_sold_reduced,
+                     bool expect_stocked_reduced,
+                     ssize_t expected_no_cat)
+
+{
+  bool no_instance;
+  ssize_t no_cat;
+  bool no_product;
+  bool lost_reduced;
+  bool sold_reduced;
+  bool stocked_reduced;
+
+  TEST_COND_RET_ON_FAIL (
+    expected_result ==
+    plugin->update_product (plugin->cls,
+                            instance->instance.id,
+                            product->id,
+                            &product->product,
+                            num_cats,
+                            cats,
+                            &no_instance,
+                            &no_cat,
+                            &no_product,
+                            &lost_reduced,
+                            &sold_reduced,
+                            &stocked_reduced),
+    "Update product failed\n");
+  if (expected_result > 0)
+  {
+    TEST_COND_RET_ON_FAIL (no_instance == expect_no_instance,
+                           "No instance wrong");
+    TEST_COND_RET_ON_FAIL (no_product == expect_no_product,
+                           "No product wrong");
+    TEST_COND_RET_ON_FAIL (lost_reduced == expect_lost_reduced,
+                           "No product wrong");
+    TEST_COND_RET_ON_FAIL (stocked_reduced == expect_stocked_reduced,
+                           "Stocked reduced wrong");
+    TEST_COND_RET_ON_FAIL (sold_reduced == expect_sold_reduced,
+                           "Sold reduced wrong");
+    TEST_COND_RET_ON_FAIL (no_cat == expected_no_cat,
+                           "Wrong category missing returned");
+  }
   return 0;
 }
 
@@ -850,25 +918,34 @@ test_lookup_product (const struct InstanceData *instance,
                      const struct ProductData *product)
 {
   struct TALER_MERCHANTDB_ProductDetails lookup_result;
+  size_t num_categories = 0;
+  uint64_t *categories = NULL;
+
   if (0 > plugin->lookup_product (plugin->cls,
                                   instance->instance.id,
                                   product->id,
-                                  &lookup_result))
+                                  &lookup_result,
+                                  &num_categories,
+                                  &categories))
   {
     GNUNET_log (GNUNET_ERROR_TYPE_ERROR,
                 "Lookup product failed\n");
     TALER_MERCHANTDB_product_details_free (&lookup_result);
     return 1;
   }
-  const struct TALER_MERCHANTDB_ProductDetails *to_cmp = &product->product;
-  if (0 != check_products_equal (&lookup_result,
-                                 to_cmp))
+  GNUNET_free (categories);
   {
-    GNUNET_break (0);
-    GNUNET_log (GNUNET_ERROR_TYPE_ERROR,
-                "Lookup product failed: incorrect product returned\n");
-    TALER_MERCHANTDB_product_details_free (&lookup_result);
-    return 1;
+    const struct TALER_MERCHANTDB_ProductDetails *to_cmp = &product->product;
+
+    if (0 != check_products_equal (&lookup_result,
+                                   to_cmp))
+    {
+      GNUNET_break (0);
+      GNUNET_log (GNUNET_ERROR_TYPE_ERROR,
+                  "Lookup product failed: incorrect product returned\n");
+      TALER_MERCHANTDB_product_details_free (&lookup_result);
+      return 1;
+    }
   }
   TALER_MERCHANTDB_product_details_free (&lookup_result);
   return 0;
@@ -1076,31 +1153,67 @@ run_test_products (struct TestProducts_Closure *cls)
   /* Test that insert without an instance fails */
   TEST_RET_ON_FAIL (test_insert_product (&cls->instance,
                                          &cls->products[0],
-                                         GNUNET_DB_STATUS_SUCCESS_NO_RESULTS));
+                                         0,
+                                         NULL,
+                                         GNUNET_DB_STATUS_SUCCESS_ONE_RESULT,
+                                         false,
+                                         true,
+                                         -1));
   /* Insert the instance */
   TEST_RET_ON_FAIL (test_insert_instance (&cls->instance,
                                           GNUNET_DB_STATUS_SUCCESS_ONE_RESULT));
   /* Test inserting a product */
   TEST_RET_ON_FAIL (test_insert_product (&cls->instance,
                                          &cls->products[0],
-                                         GNUNET_DB_STATUS_SUCCESS_ONE_RESULT));
-  /* Test that double insert fails */
+                                         0,
+                                         NULL,
+                                         GNUNET_DB_STATUS_SUCCESS_ONE_RESULT,
+                                         false,
+                                         false,
+                                         -1));
+  /* Test that double insert succeeds */
   TEST_RET_ON_FAIL (test_insert_product (&cls->instance,
                                          &cls->products[0],
-                                         GNUNET_DB_STATUS_SUCCESS_NO_RESULTS));
+                                         0,
+                                         NULL,
+                                         GNUNET_DB_STATUS_SUCCESS_ONE_RESULT,
+                                         false,
+                                         false,
+                                         -1));
+  /* Test that conflicting insert fails */
+  {
+    uint64_t cat = 42;
+
+    TEST_RET_ON_FAIL (test_insert_product (&cls->instance,
+                                           &cls->products[0],
+                                           1,
+                                           &cat,
+                                           GNUNET_DB_STATUS_SUCCESS_ONE_RESULT,
+                                           true,
+                                           false,
+                                           -1));
+  }
   /* Test lookup of individual products */
   TEST_RET_ON_FAIL (test_lookup_product (&cls->instance,
                                          &cls->products[0]));
   /* Make sure it fails correctly for products that don't exist */
-  if (GNUNET_DB_STATUS_SUCCESS_NO_RESULTS !=
-      plugin->lookup_product (plugin->cls,
-                              cls->instance.instance.id,
-                              "nonexistent_product",
-                              NULL))
   {
-    GNUNET_log (GNUNET_ERROR_TYPE_ERROR,
-                "Lookup product failed\n");
-    return 1;
+    size_t num_categories = 0;
+    uint64_t *categories = NULL;
+
+    if (GNUNET_DB_STATUS_SUCCESS_NO_RESULTS !=
+        plugin->lookup_product (plugin->cls,
+                                cls->instance.instance.id,
+                                "nonexistent_product",
+                                NULL,
+                                &num_categories,
+                                &categories))
+    {
+      GNUNET_log (GNUNET_ERROR_TYPE_ERROR,
+                  "Lookup product failed\n");
+      return 1;
+    }
+    GNUNET_free (categories);
   }
   /* Test product update */
   cls->products[0].product.description =
@@ -1126,37 +1239,76 @@ run_test_products (struct TestProducts_Closure *cls)
                  json_array_append_new (cls->products[0].product.address,
                                         json_string ("444 Some Street")));
   cls->products[0].product.next_restock = GNUNET_TIME_timestamp_get ();
-  TEST_RET_ON_FAIL (test_update_product (&cls->instance,
-                                         &cls->products[0],
-                                         GNUNET_DB_STATUS_SUCCESS_ONE_RESULT));
+  TEST_RET_ON_FAIL (test_update_product (
+                      &cls->instance,
+                      &cls->products[0],
+                      0,
+                      NULL,
+                      GNUNET_DB_STATUS_SUCCESS_ONE_RESULT,
+                      false,
+                      false,
+                      false,
+                      false,
+                      false,
+                      -1));
 
   {
     struct ProductData stock_dec = cls->products[0];
 
     stock_dec.product.total_stock = 40;
-    TEST_RET_ON_FAIL (test_update_product (&cls->instance,
-                                           &stock_dec,
-                                           GNUNET_DB_STATUS_SUCCESS_NO_RESULTS))
-    ;
+    TEST_RET_ON_FAIL (test_update_product (
+                        &cls->instance,
+                        &stock_dec,
+                        0,
+                        NULL,
+                        GNUNET_DB_STATUS_SUCCESS_ONE_RESULT,
+                        false,
+                        false,
+                        false,
+                        false,
+                        true,
+                        -1));
   }
   {
     struct ProductData lost_dec = cls->products[0];
 
     lost_dec.product.total_lost = 1;
-    TEST_RET_ON_FAIL (test_update_product (&cls->instance,
-                                           &lost_dec,
-                                           GNUNET_DB_STATUS_SUCCESS_NO_RESULTS))
-    ;
+    TEST_RET_ON_FAIL (test_update_product (
+                        &cls->instance,
+                        &lost_dec,
+                        0,
+                        NULL,
+                        GNUNET_DB_STATUS_SUCCESS_ONE_RESULT,
+                        false,
+                        false,
+                        true,
+                        false,
+                        false,
+                        -1));
   }
   TEST_RET_ON_FAIL (test_lookup_product (&cls->instance,
                                          &cls->products[0]));
-  TEST_RET_ON_FAIL (test_update_product (&cls->instance,
-                                         &cls->products[1],
-                                         GNUNET_DB_STATUS_SUCCESS_NO_RESULTS));
+  TEST_RET_ON_FAIL (test_update_product (
+                      &cls->instance,
+                      &cls->products[1],
+                      0,
+                      NULL,
+                      GNUNET_DB_STATUS_SUCCESS_ONE_RESULT,
+                      false,
+                      true,
+                      false,
+                      false,
+                      false,
+                      -1));
   /* Test collective product lookup */
   TEST_RET_ON_FAIL (test_insert_product (&cls->instance,
                                          &cls->products[1],
-                                         GNUNET_DB_STATUS_SUCCESS_ONE_RESULT));
+                                         0,
+                                         NULL,
+                                         GNUNET_DB_STATUS_SUCCESS_ONE_RESULT,
+                                         false,
+                                         false,
+                                         -1));
   TEST_RET_ON_FAIL (test_lookup_products (&cls->instance,
                                           2,
                                           cls->products));
@@ -2061,7 +2213,12 @@ run_test_orders (struct TestOrders_Closure *cls)
   /* Test order lock */
   TEST_RET_ON_FAIL (test_insert_product (&cls->instance,
                                          &cls->product,
-                                         GNUNET_DB_STATUS_SUCCESS_ONE_RESULT));
+                                         0,
+                                         NULL,
+                                         GNUNET_DB_STATUS_SUCCESS_ONE_RESULT,
+                                         false,
+                                         false,
+                                         -1));
   if (1 != plugin->insert_order_lock (plugin->cls,
                                       cls->instance.instance.id,
                                       cls->orders[0].id,
diff --git a/src/include/taler_merchant_service.h b/src/include/taler_merchant_service.h
index 24f5e61c..dc79303f 100644
--- a/src/include/taler_merchant_service.h
+++ b/src/include/taler_merchant_service.h
@@ -470,11 +470,6 @@ struct TALER_MERCHANT_InstanceInformation
    */
   const json_t *payment_targets;
 
-  /**
-   * User type for the instance.
-   */
-  enum TALER_KYCLOGIC_KycUserType ut;
-
 };
 
 
@@ -602,7 +597,6 @@ TALER_MERCHANT_instances_post (
   const char *backend_url,
   const char *instance_id,
   const char *name,
-  enum TALER_KYCLOGIC_KycUserType ut,
   const json_t *address,
   const json_t *jurisdiction,
   bool use_stefan,
@@ -668,7 +662,6 @@ TALER_MERCHANT_instance_patch (
   const char *backend_url,
   const char *instance_id,
   const char *name,
-  enum TALER_KYCLOGIC_KycUserType ut,
   const json_t *address,
   const json_t *jurisdiction,
   bool use_stefan,
@@ -790,10 +783,6 @@ struct TALER_MERCHANT_InstanceDetails
    */
   struct GNUNET_TIME_Relative default_pay_delay;
 
-  /**
-   * User type for the instance.
-   */
-  enum TALER_KYCLOGIC_KycUserType ut;
 };
 
 
@@ -1516,12 +1505,12 @@ struct TALER_MERCHANT_ProductGetResponse
       struct TALER_Amount price;
 
       /**
-       * base64-encoded product image
+       * base64-encoded product image, can be NULL if none is set.
        */
       const char *image;
 
       /**
-       * list of taxes paid by the merchant
+       * list of taxes paid by the merchant, can be NULL if no taxes were specified.
        */
       const json_t *taxes;
 
@@ -1544,7 +1533,7 @@ struct TALER_MERCHANT_ProductGetResponse
       uint64_t total_lost;
 
       /**
-       * where the product is in stock
+       * where the product is in stock, can be NULL if no location was given.
        */
       const json_t *location;
 
@@ -1707,6 +1696,54 @@ TALER_MERCHANT_products_post2 (
 
 
 /**
+ * Make a POST /products request to add a product to the
+ * inventory.
+ *
+ * @param ctx the context
+ * @param backend_url HTTP base URL for the backend
+ * @param product_id identifier to use for the product
+ * @param description description of the product
+ * @param description_i18n Map from IETF BCP 47 language tags to localized descriptions
+ * @param unit unit in which the product is measured (liters, kilograms, packages, etc.)
+ * @param price the price for one @a unit of the product, zero is used to imply that
+ *              this product is not sold separately or that the price is not fixed and
+ *              must be supplied by the front-end.  If non-zero, price must include
+ *              applicable taxes.
+ * @param image base64-encoded product image
+ * @param taxes list of taxes paid by the merchant
+ * @param total_stock in @a units, -1 to indicate "infinite" (i.e. electronic books)
+ * @param address where the product is in stock
+ * @param next_restock when the next restocking is expected to happen, 0 for unknown,
+ *                     #GNUNET_TIME_UNIT_FOREVER_ABS for 'never'.
+ * @param minimum_age minimum age the buyer must have
+ * @param num_cats length of the @a cats array
+ * @param cats array of categories the product is in
+ * @param cb function to call with the backend's result
+ * @param cb_cls closure for @a cb
+ * @return the request handle; NULL upon error
+ */
+struct TALER_MERCHANT_ProductsPostHandle *
+TALER_MERCHANT_products_post3 (
+  struct GNUNET_CURL_Context *ctx,
+  const char *backend_url,
+  const char *product_id,
+  const char *description,
+  const json_t *description_i18n,
+  const char *unit,
+  const struct TALER_Amount *price,
+  const char *image,
+  const json_t *taxes,
+  int64_t total_stock,
+  const json_t *address,
+  struct GNUNET_TIME_Timestamp next_restock,
+  uint32_t minimum_age,
+  unsigned int num_cats,
+  const uint64_t *cats,
+  TALER_MERCHANT_ProductsPostCallback cb,
+  void *cb_cls);
+
+
+/**
  * Cancel POST /products operation.
  *
  * @param pph operation to cancel
diff --git a/src/include/taler_merchantdb_lib.h b/src/include/taler_merchantdb_lib.h
index 3a641a54..a78d01f1 100644
--- a/src/include/taler_merchantdb_lib.h
+++ b/src/include/taler_merchantdb_lib.h
@@ -97,6 +97,16 @@ void
 TALER_MERCHANTDB_token_family_details_free (
   struct TALER_MERCHANTDB_TokenFamilyDetails *tf);
 
+
+/**
+ * Free members of @a cd, but not @a cd itself.
+ *
+ * @param[in] cd token family details to clean up
+ */
+void
+TALER_MERCHANTDB_category_details_free (
+  struct TALER_MERCHANTDB_CategoryDetails *cd);
+
 #endif  /* MERCHANT_DB_H */
 
 /* end of taler_merchantdb_lib.h */
diff --git a/src/include/taler_merchantdb_plugin.h b/src/include/taler_merchantdb_plugin.h
index aac39d17..f63fcd99 100644
--- a/src/include/taler_merchantdb_plugin.h
+++ b/src/include/taler_merchantdb_plugin.h
@@ -1,6 +1,6 @@
 /*
   This file is part of TALER
-  Copyright (C) 2014-2023 Taler Systems SA
+  Copyright (C) 2014-2024 Taler Systems SA
 
   TALER is free software; you can redistribute it and/or modify it under the
   terms of the GNU Lesser General Public License as published by the Free Software
@@ -210,10 +210,6 @@ struct TALER_MERCHANTDB_InstanceSettings
    */
   struct GNUNET_TIME_Relative default_pay_delay;
 
-  /**
-   * Type of user this merchant represents.
-   */
-  enum TALER_KYCLOGIC_KycUserType ut;
 };
 
 
@@ -335,6 +331,27 @@ struct TALER_MERCHANTDB_ProductDetails
 
 
 /**
+ * Typically called by `lookup_all_products`.
+ *
+ * @param cls a `json_t *` JSON array to build
+ * @param product_serial row ID of the product
+ * @param product_id ID of the product
+ * @param pd full product details
+ * @param num_categories length of @a categories array
+ * @param categories array of categories the
+ *   product is in
+ */
+typedef void
+(*TALER_MERCHANTDB_ProductCallback)(
+  void *cls,
+  uint64_t product_serial,
+  const char *product_id,
+  const struct TALER_MERCHANTDB_ProductDetails *pd,
+  size_t num_categories,
+  const uint64_t *categories);
+
+
+/**
  * Typically called by `lookup_templates`.
  *
  * @param cls closure
@@ -425,6 +442,75 @@ struct TALER_MERCHANTDB_OtpDeviceDetails
 
 
 /**
+ * Typically called by `lookup_categories`.
+ *
+ * @param cls closure
+ * @param category_id ID of the category
+ * @param category_name name of the category
+ * @param category_name_i18n translations of the @a category_name
+ * @param product_count number of products in the category
+ */
+typedef void
+(*TALER_MERCHANTDB_CategoriesCallback)(
+  void *cls,
+  uint64_t category_id,
+  const char *category_name,
+  const json_t *category_name_i18n,
+  uint64_t product_count);
+
+
+/**
+ * Details about a product category.
+ */
+struct TALER_MERCHANTDB_ProductSummary
+{
+  /**
+   * ID of the product.
+   */
+  char *product_id;
+
+  /**
+   * Description for the product.
+   */
+  char *description;
+
+  /**
+   * Translation of the @e description.
+   */
+  json_t *description_i18n;
+
+};
+
+/**
+ * Details about a product category.
+ */
+struct TALER_MERCHANTDB_CategoryDetails
+{
+
+  /**
+   * Name of the category.
+   */
+  char *category_name;
+
+  /**
+   * Translations of the name of the category.
+   */
+  json_t *category_name_i18n;
+
+  /**
+   * Products in the category.
+   */
+  struct TALER_MERCHANTDB_ProductSummary *products;
+
+  /**
+   * Length of the @e products array.
+   */
+  unsigned int num_products;
+
+};
+
+
+/**
  * Typically called by `lookup_webhooks`.
  *
  * @param cls a `json_t *` JSON array to build
@@ -1640,6 +1726,22 @@ struct TALER_MERCHANTDB_Plugin
                      TALER_MERCHANTDB_ProductsCallback cb,
                      void *cb_cls);
 
+
+  /**
+   * Lookup full details of all of the products the given instance has configured (expensive).
+   *
+   * @param cls closure
+   * @param instance_id instance to lookup products for
+   * @param cb function to call on all products found
+   * @param cb_cls closure for @a cb
+   * @return database result code
+   */
+  enum GNUNET_DB_QueryStatus
+  (*lookup_all_products)(void *cls,
+                         const char *instance_id,
+                         TALER_MERCHANTDB_ProductCallback cb,
+                         void *cb_cls);
+
   /**
    * Lookup details about a particular product.
    *
@@ -1648,13 +1750,18 @@ struct TALER_MERCHANTDB_Plugin
    * @param product_id product to lookup
    * @param[out] pd set to the product details on success, can be NULL
    *             (in that case we only want to check if the product exists)
+   * @param[out] num_categories set to length of @a categories array
+   * @param[out] categories set to array of categories the
+   *   product is in, caller must free() it.
    * @return database result code
    */
   enum GNUNET_DB_QueryStatus
   (*lookup_product)(void *cls,
                     const char *instance_id,
                     const char *product_id,
-                    struct TALER_MERCHANTDB_ProductDetails *pd);
+                    struct TALER_MERCHANTDB_ProductDetails *pd,
+                    size_t *num_categories,
+                    uint64_t **categories);
 
   /**
    * Delete information about a product. Note that the transaction must
@@ -1678,13 +1785,24 @@ struct TALER_MERCHANTDB_Plugin
    * @param instance_id instance to insert product for
    * @param product_id product identifier of product to insert
    * @param pd the product details to insert
+   * @param num_cats length of @a cats array
+   * @param cats array of categories the product is in
+   * @param[out] no_instance set to true if @a instance_id is unknown
+   * @param[out] conflict set to true if a conflicting
+   *        product already exists in the database
+   * @param[out] no_cat set to index of non-existing category from @a cats, or -1 if all @a cats were found
    * @return database result code
    */
   enum GNUNET_DB_QueryStatus
   (*insert_product)(void *cls,
                     const char *instance_id,
                     const char *product_id,
-                    const struct TALER_MERCHANTDB_ProductDetails *pd);
+                    const struct TALER_MERCHANTDB_ProductDetails *pd,
+                    size_t num_cats,
+                    const uint64_t *cats,
+                    bool *no_instance,
+                    bool *conflict,
+                    ssize_t *no_cat);
 
   /**
    * Update details about a particular product. Note that the
@@ -1695,21 +1813,31 @@ struct TALER_MERCHANTDB_Plugin
    * @param cls closure
    * @param instance_id instance to lookup products for
    * @param product_id product to lookup
-   * @param pd set to the product details on success, can be NULL
-   *             (in that case we only want to check if the product exists);
-   *             total_sold in @a pd is ignored (!), total_lost must not
-   *             exceed total_stock minus the existing total_sold;
-   *             total_sold and total_stock must be larger or equal to
-   *             the existing value;
-   * @return database result code, #GNUNET_DB_STATUS_SUCCESS_NO_RESULTS if the
-   *         non-decreasing constraints are not met *or* if the product
-   *         does not yet exist.
+   * @param pd product details with updated values
+   * @param num_cats length of @a cats array
+   * @param cats number of categories the product is in
+   * @param[out] no_instance the update failed as the instance is unknown
+   * @param[out] no_cat set to -1 on success, otherwise the update failed and this is set
+   *                to the index of a category in @a cats that is unknown
+   * @param[out] no_product the @a product_id is unknown
+   * @param[out] lost_reduced the update failed as the counter of units lost would have been lowered
+   * @param[out] sold_reduced the update failed as the counter of units sold would have been lowered
+   * @param[out] stocked_reduced the update failed as the counter of units stocked would have been lowered
+   * @return database result code
    */
   enum GNUNET_DB_QueryStatus
   (*update_product)(void *cls,
                     const char *instance_id,
                     const char *product_id,
-                    const struct TALER_MERCHANTDB_ProductDetails *pd);
+                    const struct TALER_MERCHANTDB_ProductDetails *pd,
+                    size_t num_cats,
+                    const uint64_t *cats,
+                    bool *no_instance,
+                    ssize_t *no_cat,
+                    bool *no_product,
+                    bool *lost_reduced,
+                    bool *sold_reduced,
+                    bool *stocked_reduced);
 
   /**
    * Lock stocks of a particular product. Note that the transaction must
@@ -2920,6 +3048,24 @@ struct TALER_MERCHANTDB_Plugin
 
 
   /**
+   * Update details about a particular template.
+   *
+   * @param cls closure
+   * @param instance_id instance to update template for
+   * @param template_id template to update
+   * @param td update to the template details on success, can be NULL
+   *             (in that case we only want to check if the template exists)
+   * @return database result code, #GNUNET_DB_STATUS_SUCCESS_NO_RESULTS if the template
+   *         does not yet exist.
+   */
+  enum GNUNET_DB_QueryStatus
+  (*update_template)(void *cls,
+                     const char *instance_id,
+                     const char *template_id,
+                     const struct TALER_MERCHANTDB_TemplateDetails *td);
+
+
+  /**
    * Delete information about an OTP device.
    *
    * @param cls closure
@@ -3015,21 +3161,104 @@ struct TALER_MERCHANTDB_Plugin
 
 
   /**
-   * Update details about a particular template.
+   * Delete information about a product category.
    *
    * @param cls closure
-   * @param instance_id instance to update template for
-   * @param template_id template to update
-   * @param td update to the template details on success, can be NULL
-   *             (in that case we only want to check if the template exists)
+   * @param instance_id instance to delete category of
+   * @param category_id identifies the category to delete
+   * @return DB status code, #GNUNET_DB_STATUS_SUCCESS_NO_RESULTS
+   *           if template unknown.
+   */
+  enum GNUNET_DB_QueryStatus
+  (*delete_category)(void *cls,
+                     const char *instance_id,
+                     uint64_t category_id);
+
+  /**
+   * Insert new product category.
+   *
+   * @param cls closure
+   * @param instance_id instance to insert OTP device for
+   * @param category_name name of the category
+   * @param category_name_i18n translations of the category name
+   * @param[out] category_id set to the category id on success
+   * @return database result code
+   */
+  enum GNUNET_DB_QueryStatus
+  (*insert_category)(void *cls,
+                     const char *instance_id,
+                     const char *category_name,
+                     const json_t *category_name_i18n,
+                     uint64_t *category_id);
+
+
+  /**
+   * Update descriptions of a product category.
+   *
+   * @param cls closure
+   * @param instance_id instance to update OTP device for
+   * @param category_id category to update
+   * @param category_name name of the category
+   * @param category_name_i18n translations of the category name
    * @return database result code, #GNUNET_DB_STATUS_SUCCESS_NO_RESULTS if the template
    *         does not yet exist.
    */
   enum GNUNET_DB_QueryStatus
-  (*update_template)(void *cls,
+  (*update_category)(void *cls,
                      const char *instance_id,
-                     const char *template_id,
-                     const struct TALER_MERCHANTDB_TemplateDetails *td);
+                     uint64_t category_id,
+                     const char *category_name,
+                     const json_t *category_name_i18n);
+
+  /**
+   * Lookup all of the product categories the given instance has configured.
+   *
+   * @param cls closure
+   * @param instance_id instance to lookup OTP devices for
+   * @param cb function to call on all categories found
+   * @param cb_cls closure for @a cb
+   * @return database result code
+   */
+  enum GNUNET_DB_QueryStatus
+  (*lookup_categories)(void *cls,
+                       const char *instance_id,
+                       TALER_MERCHANTDB_CategoriesCallback cb,
+                       void *cb_cls);
+
+
+  /**
+   * Lookup details about product category.
+   *
+   * @param cls closure
+   * @param instance_id instance to lookup template for
+   * @param category_id category to update
+   * @param[out] cd set to the category details on success, can be NULL
+   *             (in that case we only want to check if the category exists)
+   * @return database result code
+   */
+  enum GNUNET_DB_QueryStatus
+  (*select_category)(void *cls,
+                     const char *instance_id,
+                     uint64_t category_id,
+                     struct TALER_MERCHANTDB_CategoryDetails *cd);
+
+
+  /**
+   * Lookup details about product category by name.
+   *
+   * @param cls closure
+   * @param instance_id instance to lookup template for
+   * @param category_name category name to look for
+   * @param[out] name_i18n category name translation
+   * @param[out] category_id category ID
+   * @return database result code
+   */
+  enum GNUNET_DB_QueryStatus
+  (*select_category_by_name)(void *cls,
+                             const char *instance_id,
+                             const char *category_name,
+                             json_t **name_i18n,
+                             uint64_t *category_id);
 
 
   /**
diff --git a/src/lib/Makefile.am b/src/lib/Makefile.am
index 1e7430d4..4e6a901a 100644
--- a/src/lib/Makefile.am
+++ b/src/lib/Makefile.am
@@ -10,7 +10,7 @@ lib_LTLIBRARIES = \
   libtalermerchant.la
 
 libtalermerchant_la_LDFLAGS = \
-  -version-info 5:2:0 \
+  -version-info 6:0:0 \
   -no-undefined
 
 libtalermerchant_la_SOURCES = \
diff --git a/src/lib/merchant_api_get_config.c b/src/lib/merchant_api_get_config.c
index b4b700bd..9b501342 100644
--- a/src/lib/merchant_api_get_config.c
+++ b/src/lib/merchant_api_get_config.c
@@ -34,12 +34,12 @@
  * Which version of the Taler protocol is implemented
  * by this library?  Used to determine compatibility.
  */
-#define MERCHANT_PROTOCOL_CURRENT 14
+#define MERCHANT_PROTOCOL_CURRENT 16
 
 /**
  * How many configs are we backwards-compatible with?
  */
-#define MERCHANT_PROTOCOL_AGE 2
+#define MERCHANT_PROTOCOL_AGE 4
 
 /**
  * How many exchanges do we allow at most per merchant?
diff --git a/src/lib/merchant_api_get_instance.c b/src/lib/merchant_api_get_instance.c
index eef95b84..76f3691a 100644
--- a/src/lib/merchant_api_get_instance.c
+++ b/src/lib/merchant_api_get_instance.c
@@ -136,16 +136,6 @@ handle_get_instance_finished (void *cls,
       }
       igr.details.ok.details.address = address;
       igr.details.ok.details.jurisdiction = jurisdiction;
-      if (GNUNET_OK !=
-          TALER_KYCLOGIC_kyc_user_type_from_string (
-                                                    uts,
-                                                    &igr.details.ok.details.ut))
-      {
-        GNUNET_break_op (0);
-        igr.hr.http_status = 0;
-        igr.hr.ec = TALER_EC_GENERIC_INVALID_RESPONSE;
-        break;
-      }
       igh->cb (igh->cb_cls,
                &igr);
       TALER_MERCHANT_instance_get_cancel (igh);
diff --git a/src/lib/merchant_api_get_instances.c b/src/lib/merchant_api_get_instances.c
index b2f99853..c47c4895 100644
--- a/src/lib/merchant_api_get_instances.c
+++ b/src/lib/merchant_api_get_instances.c
@@ -126,13 +126,6 @@ parse_instances (const json_t *json,
         GNUNET_break_op (0);
         return GNUNET_SYSERR;
       }
-      if (GNUNET_OK !=
-          TALER_KYCLOGIC_kyc_user_type_from_string (uts,
-                                                    &ii->ut))
-      {
-        GNUNET_break_op (0);
-        return GNUNET_SYSERR;
-      }
       for (size_t i = 0; i<json_array_size (ii->payment_targets); i++)
       {
         if  (! json_is_string (json_array_get (ii->payment_targets,
diff --git a/src/lib/merchant_api_get_product.c b/src/lib/merchant_api_get_product.c
index 3f026bf3..bb10a438 100644
--- a/src/lib/merchant_api_get_product.c
+++ b/src/lib/merchant_api_get_product.c
@@ -1,6 +1,6 @@
 /*
   This file is part of TALER
-  Copyright (C) 2014-2023 Taler Systems SA
+  Copyright (C) 2014-2024 Taler Systems SA
 
   TALER is free software; you can redistribute it and/or modify it under the
   terms of the GNU Lesser General Public License as published by the Free Software
@@ -105,12 +105,16 @@ handle_get_product_finished (void *cls,
         TALER_JSON_spec_amount_any (
           "price",
           &pgr.details.ok.price),
-        GNUNET_JSON_spec_string (
-          "image",
-          &pgr.details.ok.image),
-        GNUNET_JSON_spec_array_const (
-          "taxes",
-          &pgr.details.ok.taxes),
+        GNUNET_JSON_spec_mark_optional (
+          GNUNET_JSON_spec_string (
+            "image",
+            &pgr.details.ok.image),
+          NULL),
+        GNUNET_JSON_spec_mark_optional (
+          GNUNET_JSON_spec_array_const (
+            "taxes",
+            &pgr.details.ok.taxes),
+          NULL),
         GNUNET_JSON_spec_int64 (
           "total_stock",
           &pgr.details.ok.total_stock),
@@ -120,12 +124,15 @@ handle_get_product_finished (void *cls,
         GNUNET_JSON_spec_uint64 (
           "total_lost",
           &pgr.details.ok.total_lost),
-        GNUNET_JSON_spec_object_const (
-          "address",
-          &pgr.details.ok.location),
         GNUNET_JSON_spec_mark_optional (
-          GNUNET_JSON_spec_timestamp ("next_restock",
-                                      &pgr.details.ok.next_restock),
+          GNUNET_JSON_spec_object_const (
+            "address",
+            &pgr.details.ok.location),
+          NULL),
+        GNUNET_JSON_spec_mark_optional (
+          GNUNET_JSON_spec_timestamp (
+            "next_restock",
+            &pgr.details.ok.next_restock),
           NULL),
         GNUNET_JSON_spec_end ()
       };
diff --git a/src/lib/merchant_api_patch_instance.c b/src/lib/merchant_api_patch_instance.c
index 420cd549..f4f39642 100644
--- a/src/lib/merchant_api_patch_instance.c
+++ b/src/lib/merchant_api_patch_instance.c
@@ -159,7 +159,6 @@ TALER_MERCHANT_instance_patch (
   const char *backend_url,
   const char *instance_id,
   const char *name,
-  enum TALER_KYCLOGIC_KycUserType ut,
   const json_t *address,
   const json_t *jurisdiction,
   bool use_stefan,
@@ -170,19 +169,10 @@ TALER_MERCHANT_instance_patch (
 {
   struct TALER_MERCHANT_InstancePatchHandle *iph;
   json_t *req_obj;
-  const char *uts;
 
-  uts = TALER_KYCLOGIC_kyc_user_type2s (ut);
-  if (NULL == uts)
-  {
-    GNUNET_break (0);
-    return NULL;
-  }
   req_obj = GNUNET_JSON_PACK (
     GNUNET_JSON_pack_string ("name",
                              name),
-    GNUNET_JSON_pack_string ("user_type",
-                             uts),
     GNUNET_JSON_pack_object_incref ("address",
                                     (json_t *) address),
     GNUNET_JSON_pack_object_incref ("jurisdiction",
diff --git a/src/lib/merchant_api_post_instances.c b/src/lib/merchant_api_post_instances.c
index 73d36369..c8e5add6 100644
--- a/src/lib/merchant_api_post_instances.c
+++ b/src/lib/merchant_api_post_instances.c
@@ -165,7 +165,6 @@ TALER_MERCHANT_instances_post (
   const char *backend_url,
   const char *instance_id,
   const char *name,
-  enum TALER_KYCLOGIC_KycUserType ut,
   const json_t *address,
   const json_t *jurisdiction,
   bool use_stefan,
@@ -178,14 +177,7 @@ TALER_MERCHANT_instances_post (
   struct TALER_MERCHANT_InstancesPostHandle *iph;
   json_t *req_obj;
   json_t *auth_obj;
-  const char *uts;
 
-  uts = TALER_KYCLOGIC_kyc_user_type2s (ut);
-  if (NULL == uts)
-  {
-    GNUNET_break (0);
-    return NULL;
-  }
   if (NULL != auth_token)
   {
     if (0 != strncasecmp (RFC_8959_PREFIX,
@@ -219,8 +211,6 @@ TALER_MERCHANT_instances_post (
                              instance_id),
     GNUNET_JSON_pack_string ("name",
                              name),
-    GNUNET_JSON_pack_string ("user_type",
-                             uts),
     GNUNET_JSON_pack_object_incref ("address",
                                     (json_t *) address),
     GNUNET_JSON_pack_object_incref ("jurisdiction",
diff --git a/src/lib/merchant_api_post_products.c b/src/lib/merchant_api_post_products.c
index 0f09f397..5d0ad27e 100644
--- a/src/lib/merchant_api_post_products.c
+++ b/src/lib/merchant_api_post_products.c
@@ -159,7 +159,7 @@ handle_post_products_finished (void *cls,
 
 
 struct TALER_MERCHANT_ProductsPostHandle *
-TALER_MERCHANT_products_post2 (
+TALER_MERCHANT_products_post3 (
   struct GNUNET_CURL_Context *ctx,
   const char *backend_url,
   const char *product_id,
@@ -173,12 +173,28 @@ TALER_MERCHANT_products_post2 (
   const json_t *address,
   struct GNUNET_TIME_Timestamp next_restock,
   uint32_t minimum_age,
+  unsigned int num_cats,
+  const uint64_t *cats,
   TALER_MERCHANT_ProductsPostCallback cb,
   void *cb_cls)
 {
   struct TALER_MERCHANT_ProductsPostHandle *pph;
   json_t *req_obj;
+  json_t *categories;
 
+  if (0 == num_cats)
+  {
+    categories = NULL;
+  }
+  else
+  {
+    categories = json_array ();
+    GNUNET_assert (NULL != categories);
+    for (unsigned int i = 0; i<num_cats; i++)
+      GNUNET_assert (0 ==
+                     json_array_append_new (categories,
+                                            json_integer (cats[i])));
+  }
   req_obj = GNUNET_JSON_PACK (
     GNUNET_JSON_pack_string ("product_id",
                              product_id),
@@ -187,6 +203,9 @@ TALER_MERCHANT_products_post2 (
     GNUNET_JSON_pack_allow_null (
       GNUNET_JSON_pack_object_incref ("description_i18n",
                                       (json_t *) description_i18n)),
+    GNUNET_JSON_pack_allow_null (
+      GNUNET_JSON_pack_array_steal ("categories",
+                                    categories)),
     GNUNET_JSON_pack_string ("unit",
                              unit),
     TALER_JSON_pack_amount ("price",
@@ -243,6 +262,44 @@ TALER_MERCHANT_products_post2 (
 
 
 struct TALER_MERCHANT_ProductsPostHandle *
+TALER_MERCHANT_products_post2 (
+  struct GNUNET_CURL_Context *ctx,
+  const char *backend_url,
+  const char *product_id,
+  const char *description,
+  const json_t *description_i18n,
+  const char *unit,
+  const struct TALER_Amount *price,
+  const char *image,
+  const json_t *taxes,
+  int64_t total_stock,
+  const json_t *address,
+  struct GNUNET_TIME_Timestamp next_restock,
+  uint32_t minimum_age,
+  TALER_MERCHANT_ProductsPostCallback cb,
+  void *cb_cls)
+{
+  return TALER_MERCHANT_products_post3 (ctx,
+                                        backend_url,
+                                        product_id,
+                                        description,
+                                        description_i18n,
+                                        unit,
+                                        price,
+                                        image,
+                                        taxes,
+                                        total_stock,
+                                        address,
+                                        next_restock,
+                                        minimum_age,
+                                        0,
+                                        NULL,
+                                        cb,
+                                        cb_cls);
+}
+
+
+struct TALER_MERCHANT_ProductsPostHandle *
 TALER_MERCHANT_products_post (
   struct GNUNET_CURL_Context *ctx,
   const char *backend_url,
diff --git a/src/merchant-tools/taler-merchant-passwd.c b/src/merchant-tools/taler-merchant-passwd.c
index bfd6534d..bcb856e5 100644
--- a/src/merchant-tools/taler-merchant-passwd.c
+++ b/src/merchant-tools/taler-merchant-passwd.c
@@ -54,7 +54,7 @@ run (void *cls,
   const char *pw = args[0];
   struct TALER_MERCHANTDB_InstanceAuthSettings ias;
   enum GNUNET_DB_QueryStatus qs;
-  
+
   if (NULL == pw)
     pw = getenv ("TALER_MERCHANT_PASSWORD");
   if (NULL == pw)
@@ -64,6 +64,16 @@ run (void *cls,
     global_ret = -1;
     return;
   }
+  if (0 != strncmp (pw,
+                    RFC_8959_PREFIX,
+                    strlen (RFC_8959_PREFIX)))
+  {
+    fprintf (stderr,
+             "Invalid password specified, does not begin with `%s'\n",
+             RFC_8959_PREFIX);
+    global_ret = 1;
+    return;
+  }
   if (NULL == instance)
     instance = GNUNET_strdup ("default");
   cfg = GNUNET_CONFIGURATION_dup (config);
@@ -112,7 +122,7 @@ run (void *cls,
         .size = ntohs (sizeof (es)),
         .type = ntohs (TALER_DBEVENT_MERCHANT_INSTANCE_SETTINGS)
       };
-      
+
       plugin->event_notify (plugin->cls,
                             &es,
                             instance,
diff --git a/src/testing/test_merchant_order_creation.sh b/src/testing/test_merchant_order_creation.sh
index 0869cfdd..1b52b4af 100755
--- a/src/testing/test_merchant_order_creation.sh
+++ b/src/testing/test_merchant_order_creation.sh
@@ -263,7 +263,7 @@ echo " OK"
 
 echo -n "Creating v1 order with token family ..."
 STATUS=$(curl 'http://localhost:9966/private/orders' \
-    -d '{"order":{"version":"1","amount":"TESTKUDOS:7","summary":"with_subscription","fulfillment_message":"Payed successfully","choices":[{"inputs":[{"kind":"token","count":1,"token_family_slug":"test-sub","valid_after":{"t_s":'$NOW'}}],"outputs":[{"kind":"token","count":1,"token_family_slug":"test-sub","valid_after":{"t_s":'$NOW'}}]}]}}' \
+    -d '{"order":{"version":"1","amount":"TESTKUDOS:7","summary":"with_subscription","fulfillment_message":"Paid successfully","choices":[{"inputs":[{"kind":"token","count":1,"token_family_slug":"test-sub","valid_after":{"t_s":'$NOW'}}],"outputs":[{"kind":"token","count":1,"token_family_slug":"test-sub","valid_after":{"t_s":'$NOW'}}]}]}}' \
     -w "%{http_code}" -s -o "$LAST_RESPONSE")
 
 if [ "$STATUS" != "200" ]
diff --git a/src/testing/test_merchant_order_refund.sh b/src/testing/test_merchant_order_refund.sh
new file mode 100755
index 00000000..af07d233
--- /dev/null
+++ b/src/testing/test_merchant_order_refund.sh
@@ -0,0 +1,233 @@
+#!/bin/bash
+#!/bin/bash
+# This file is in the public domain.
+
+set -eu
+
+function clean_wallet() {
+    echo rm -f "${WALLET_DB}"
+    exit_cleanup
+}
+
+
+# Replace with 0 for nexus...
+USE_FAKEBANK=1
+if [ 1 = "$USE_FAKEBANK" ]
+then
+    ACCOUNT="exchange-account-2"
+    BANK_FLAGS="-f -d x-taler-bank -u $ACCOUNT"
+    BANK_URL="http://localhost:8082/"
+else
+    ACCOUNT="exchange-account-1"
+    BANK_FLAGS="-ns -d iban -u $ACCOUNT"
+    BANK_URL="http://localhost:18082/"
+    echo -n "Testing for libeufin-bank"
+    libeufin-bank --help >/dev/null </dev/null || exit_skip " MISSING"
+    echo " FOUND"
+
+fi
+
+. setup.sh
+
+echo -n "Testing for taler-harness"
+taler-harness --help >/dev/null </dev/null || exit_skip " MISSING"
+echo " FOUND"
+
+# Launch exchange, merchant and bank.
+setup -c "test_template.conf" \
+      -em \
+      $BANK_FLAGS
+LAST_RESPONSE=$(mktemp -p "${TMPDIR:-/tmp}" test_response.conf-XXXXXX)
+CONF="test_template.conf.edited"
+WALLET_DB=$(mktemp -p "${TMPDIR:-/tmp}" test_wallet.json-XXXXXX)
+EXCHANGE_URL="http://localhost:8081/"
+
+# Install cleanup handler (except for kill -9)
+trap clean_wallet EXIT
+
+echo -n "First prepare wallet with coins ..."
+rm -f "$WALLET_DB"
+taler-wallet-cli \
+    --no-throttle \
+    --wallet-db="$WALLET_DB" \
+    api \
+    --expect-success 'withdrawTestBalance' \
+  "$(jq -n '
+    {
+        amount: "TESTKUDOS:99",
+        corebankApiBaseUrl: $BANK_URL,
+        exchangeBaseUrl: $EXCHANGE_URL
+    }' \
+    --arg BANK_URL "${BANK_URL}" \
+    --arg EXCHANGE_URL "$EXCHANGE_URL"
+  )" 2>wallet-withdraw-1.err >wallet-withdraw-1.out
+echo -n "."
+# FIXME-MS: add logic to have nexus check immediately here.
+# sleep 10
+echo -n "."
+# NOTE: once libeufin can do long-polling, we should
+# be able to reduce the delay here and run wirewatch
+# always in the background via setup
+taler-exchange-wirewatch \
+    -a "$ACCOUNT" \
+    -L "INFO" \
+    -c "$CONF" \
+    -t &> taler-exchange-wirewatch.out
+echo -n "."
+taler-wallet-cli \
+    --wallet-db="$WALLET_DB" \
+    run-until-done \
+    2>wallet-withdraw-finish-1.err \
+    >wallet-withdraw-finish-1.out
+echo " OK"
+
+CURRENCY_COUNT=$(taler-wallet-cli --wallet-db="$WALLET_DB" balance | jq '.balances|length')
+if [ "$CURRENCY_COUNT" = "0" ]
+then
+    exit_fail "Expected least one currency, withdrawal failed. check log."
+fi
+
+#
+# CREATE INSTANCE FOR TESTING
+#
+
+echo -n "Configuring merchant instance ..."
+
+STATUS=$(curl -H "Content-Type: application/json" -X POST \
+    -H 'Authorization: Bearer secret-token:super_secret' \
+    http://localhost:9966/management/instances \
+    -d '{"auth":{"method":"external"},"id":"default","name":"default","user_type":"business","address":{},"jurisdiction":{},"use_stefan":true,"default_wire_transfer_delay":{"d_us" : 50000000000},"default_pay_delay":{"d_us": 60000000000}}' \
+    -w "%{http_code}" -s -o /dev/null)
+
+if [ "$STATUS" != "204" ]
+then
+    exit_fail "Expected '204 No content' response. Got instead $STATUS"
+fi
+echo "Ok"
+
+echo -n "Configuring merchant account ..."
+
+if [ 1 = "$USE_FAKEBANK" ]
+then
+    FORTYTHREE="payto://x-taler-bank/localhost/fortythree?receiver-name=fortythree"
+else
+    FORTYTHREE=$(get_payto_uri fortythree x)
+fi
+# create with 2 bank account addresses
+STATUS=$(curl -H "Content-Type: application/json" -X POST \
+    -H 'Authorization: Bearer secret-token:super_secret' \
+    http://localhost:9966/private/accounts \
+    -d '{"payto_uri":"'"$FORTYTHREE"'"}' \
+    -w "%{http_code}" -s -o /dev/null)
+
+if [ "$STATUS" != "200" ]
+then
+    exit_fail "Expected '200 OK' response. Got instead $STATUS"
+fi
+
+echo "Ok"
+
+
+#
+# CREATE ORDER AND SELL IT
+#
+
+echo -n "Creating order to be paid..."
+STATUS=$(curl 'http://localhost:9966/private/orders' \
+    -d '{"order":{"amount":"TESTKUDOS:5","summary":"payme","auto_refund":{"d_us":180000000}}}' \
+    -w "%{http_code}" -s -o "$LAST_RESPONSE")
+
+if [ "$STATUS" != "200" ]
+then
+    jq . < "$LAST_RESPONSE"
+    exit_fail "Expected 200, order created. got: $STATUS"
+fi
+
+ORDER_ID=$(jq -e -r .order_id < "$LAST_RESPONSE")
+TOKEN=$(jq -e -r .token < "$LAST_RESPONSE")
+
+STATUS=$(curl "http://localhost:9966/private/orders/${ORDER_ID}" \
+    -w "%{http_code}" -s -o "$LAST_RESPONSE")
+
+if [ "$STATUS" != "200" ]
+then
+    jq . < "$LAST_RESPONSE"
+    exit_fail "Expected 200, getting order info before claming it. got: $STATUS"
+fi
+
+PAY_URL=$(jq -e -r .taler_pay_uri < "$LAST_RESPONSE")
+
+echo "OK"
+
+#
+# PAY THE ORDER
+#
+# set -x
+PAYMENT_START=$(date +%s)
+echo "Pay first order ${PAY_URL} ..."
+taler-wallet-cli --no-throttle -V --wallet-db="$WALLET_DB" handle-uri "${PAY_URL}" -y 2> wallet-pay1.err > wallet-pay1.log
+PAYMENT_END=$(date +%s)
+echo " OK (payment took $(( PAYMENT_END - PAYMENT_START )) secs )"
+
+STATUS=$(curl "http://localhost:9966/private/orders/${ORDER_ID}" \
+    -w "%{http_code}" -s -o "$LAST_RESPONSE")
+
+if [ "$STATUS" != "200" ]
+then
+    jq . < "$LAST_RESPONSE"
+    exit_fail "Expected 200, after pay. got: $STATUS"
+fi
+
+ORDER_STATUS=$(jq -r .order_status < "$LAST_RESPONSE")
+
+if [ "$ORDER_STATUS" != "paid" ]
+then
+    jq . < "$LAST_RESPONSE"
+    exit_fail "Order status should be 'paid'. got: $ORDER_STATUS"
+fi
+
+
+echo Sending refund for TESTKUDOS:1
+
+STATUS=$(curl "http://localhost:9966/private/orders/${ORDER_ID}/refund" \
+    -d '{"refund":"TESTKUDOS:1","reason":"duplicated"}' \
+    -w "%{http_code}" -s -o "$LAST_RESPONSE")
+  
+if [ "$STATUS" != "200" ]
+then
+    jq . < "$LAST_RESPONSE"
+    exit_fail "Expected 200, after refund. got: $STATUS"
+fi
+
+REFUND_URI=$(jq -e -r .taler_refund_uri < "$LAST_RESPONSE")
+
+REFUND_START=$(date +%s)
+echo "First refund order ${REFUND_URI} ..."
+set -x
+taler-wallet-cli --no-throttle --wallet-db="$WALLET_DB" handle-uri "${REFUND_URI}" -y 2> wallet-refund1.err > wallet-refund1.log
+taler-wallet-cli --no-throttle --wallet-db="$WALLET_DB" run-pending -y 2> wallet-pending-refund1.err > wallet-pending-refund1.log
+REFUND_END=$(date +%s)
+echo " OK (refund1 took $(( REFUND_END - REFUND_START )) secs )"
+
+echo Increasing refund for TESTKUDOS:3
+
+STATUS=$(curl "http://localhost:9966/private/orders/${ORDER_ID}/refund" \
+    -d '{"refund":"TESTKUDOS:5","reason":"duplicated"}' \
+    -w "%{http_code}" -s -o "$LAST_RESPONSE")
+  
+if [ "$STATUS" != "200" ]
+then
+    jq . < "$LAST_RESPONSE"
+    exit_fail "Expected 200, after refund. got: $STATUS"
+fi
+
+REFUND_URI=$(jq -e -r .taler_refund_uri < "$LAST_RESPONSE")
+
+REFUND2_START=$(date +%s)
+echo "Second refund order ${REFUND_URI} ..."
+taler-wallet-cli --no-throttle --wallet-db="$WALLET_DB" handle-uri "${REFUND_URI}" -y 2> wallet-refund2.err > wallet-refund2.log
+taler-wallet-cli --no-throttle --wallet-db="$WALLET_DB" run-pending -y 2> wallet-pending-refund2.err > wallet-pending-refund2.log
+REFUND2_END=$(date +%s)
+echo " OK (refund2 took $(( REFUND2_END - REFUND_START )) secs )"
+
+exit 0
diff --git a/src/testing/testing_api_cmd_patch_instance.c b/src/testing/testing_api_cmd_patch_instance.c
index cef38bec..f4ae5cf7 100644
--- a/src/testing/testing_api_cmd_patch_instance.c
+++ b/src/testing/testing_api_cmd_patch_instance.c
@@ -158,7 +158,6 @@ patch_instance_run (void *cls,
     pis->merchant_url,
     pis->instance_id,
     pis->name,
-    TALER_KYCLOGIC_KYC_UT_BUSINESS,
     pis->address,
     pis->jurisdiction,
     pis->use_stefan,
diff --git a/src/testing/testing_api_cmd_post_instances.c b/src/testing/testing_api_cmd_post_instances.c
index 0d081026..18afb2e8 100644
--- a/src/testing/testing_api_cmd_post_instances.c
+++ b/src/testing/testing_api_cmd_post_instances.c
@@ -164,7 +164,6 @@ post_instances_run (void *cls,
     pis->merchant_url,
     pis->instance_id,
     pis->name,
-    TALER_KYCLOGIC_KYC_UT_BUSINESS,
     pis->address,
     pis->jurisdiction,
     pis->use_stefan,