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+# Wiring
+
+The diagram is incomplete. The following things aren't shown on the diagram:
+
+ - [ ] Device Messages
+ - [ ] User Profiles
+ - [ ] Notification Counts
+ - [ ] Sending federation.
+ - [ ] Querying federation.
+ - [ ] Other things that aren't shown on the diagram.
+
+Diagram:
+
+
+    W -> Writer
+    S -> Server/Store/Service/Something/Stuff
+    R -> Reader
+
+               +---+                                                    +---+                              +---+
+    +----------| W |                                         +----------| S |                     +--------| R |
+    |          +---+                                         | Receipts +---+                     | Client +---+
+    | Federation |>=========================================>| Server     |>=====================>| Sync     |
+    | Send       |                                           |            |                       |          |
+    |            |                                 +---+     |            |                       |          |
+    |            |                        +--------| W |     |            |                       |          |
+    |            |                        | Client +---+     |            |                       |          |
+    |            |                        | Receipt  |>=====>|            |                       |          |
+    |            |                        | Updater  |       |            |                       |          |
+    |            |                        +----------+       |            |                       |          |
+    |            |                                           |            |                       |          |
+    |            |                +---+            +---+     |            |                +---+  |          |
+    |            |   +------------| W |     +------| S |     |            |       +--------| R |  |          |
+    |            |   | Federation +---+     | Room +---+     |            |       | Client +---+  |          |
+    |            |   | Backfill     |>=====>| Server |>=====>|            |>=====>| Push     |    |          |
+    |            |   +--------------+       |        |       +------------+       |          |    |          |
+    |            |                          |        |                            |          |    |          |
+    |            |                          |        |>==========================>|          |    |          |
+    |            |                          |        |                            +----------+    |          |
+    |            |                          |        |                                            |          |
+    |            |                          |        |                                     +---+  |          |
+    |            |                          |        |                            +--------| R |  |          |
+    |            |                          |        |                            | Client +---+  |          |
+    |            |>========================>|        |>==========================>| Search   |    |          |
+    |            |                          |        |                            |          |    |          |
+    |            |                          |        |                            +----------+    |          |
+    |            |                          |        |                                            |          |
+    |            |                          |        |>==========================================>|          |
+    |            |                          |        |                                            |          |
+    |            |                +---+     |        |                  +---+                     |          |
+    |            |       +--------| W |     |        |       +----------| S |                     |          |
+    |            |       | Client +---+     |        |       | Presence +---+                     |          |
+    |            |       | Room     |>=====>|        |>=====>| Server     |>=====================>|          |
+    |            |       | Send     |       +--------+       |            |                       |          |
+    |            |       |          |                        |            |                       |          |
+    |            |       |          |>======================>|            |<=====================<|          |
+    |            |       +----------+                        |            |                       |          |
+    |            |                                           |            |                       |          |
+    |            |                                 +---+     |            |                       |          |
+    |            |                        +--------| W |     |            |                       |          |
+    |            |                        | Client +---+     |            |                       |          |
+    |            |                        | Presence |>=====>|            |                       |          |
+    |            |                        | Setter   |       |            |                       |          |
+    |            |                        +----------+       |            |                       |          |
+    |            |                                           |            |                       |          |
+    |            |                                           |            |                       |          |
+    |            |>=========================================>|            |                       |          |
+    |            |                                           +------------+                       |          |
+    |            |                                                                                |          |
+    |            |                                                      +---+                     |          |
+    |            |                                           +----------| S |                     |          |
+    |            |                                           | Typing   +---+                     |          |
+    |            |>=========================================>| Server     |>=====================>|          |
+    +------------+                                           |            |                       +----------+
+                                                   +---+     |            |
+                                          +--------| W |     |            |
+                                          | Client +---+     |            |
+                                          | Typing   |>=====>|            |
+                                          | Setter   |       |            |
+                                          +----------+       +------------+
+
+
+# Component Descriptions
+
+Many of the components are logical rather than physical. For example it is
+possible that all of the client API writers will end up being glued together
+and always deployed as a single unit.
+
+Outbound federation requests will probably need to be funnelled through a
+choke-point to implement ratelimiting and backoff correctly.
+
+## Federation Send
+
+ * Handles `/federation/v1/send/` requests.
+ * Fetches missing ``prev_events`` from the remote server if needed.
+ * Fetches missing room state from the remote server if needed.
+ * Checks signatures on remote events, downloading keys if needed.
+ * Queries information needed to process events from the Room Server.
+ * Writes room events to logs.
+ * Writes presence updates to logs.
+ * Writes receipt updates to logs.
+ * Writes typing updates to logs.
+ * Writes other updates to logs.
+
+## Client Room Send
+
+ * Handles puts to `/client/v1/rooms/` that create room events.
+ * Queries information needed to process events from the Room Server.
+ * Talks to remote servers if needed for joins and invites.
+ * Writes room event pdus.
+ * Writes presence updates to logs.
+
+## Client Presence Setter
+
+ * Handles puts to whatever the client API path for presence is?
+ * Writes presence updates to logs.
+
+## Client Typing Setter
+
+ * Handles puts to whatever the client API path for typing is?
+ * Writes typing updates to logs.
+
+## Client Receipt Updater
+
+ * Handles puts to whatever the client API path for receipts is?
+ * Writes typing updates to logs.
+
+## Federation Backfill
+
+ * Backfills events from other servers
+ * Writes the resulting room events to logs.
+ * Is a different component from the room server itself cause it'll
+   be easier if the room server component isn't making outbound HTTP requests
+   to remote servers
+
+## Room Server
+
+ * Reads new and backfilled room events from the logs written by FS, FB and CRS.
+ * Tracks the current state of the room and the state at each event.
+ * Probably does auth checks on the incoming events.
+ * Handles state resolution as part of working out the current state and the
+ * state at each event.
+ * Writes updates to the current state and new events to logs.
+ * Shards by room ID.
+
+## Receipt Server
+
+ * Reads new updates to receipts from the logs written by the FS and CRU.
+ * Somehow learns enough information from the room server to workout how the
+   current receipt markers move with each update.
+ * Writes the new marker positions to logs
+ * Shards by room ID?
+ * It may be impossible to implement without folding it into the Room Server
+   forever coupling the components together.
+
+## Typing Server
+
+ * Reads new updates to typing from the logs written by the FS and CTS.
+ * Updates the current list of people typing in a room.
+ * Writes the current list of people typing in a room to the logs.
+ * Shards by room ID?
+
+## Presence Server
+
+ * Reads the current state of the rooms from the logs to track the intersection
+   of room membership between users.
+ * Reads updates to presence from the logs writen by the FS and the CPS.
+ * Reads when clients sync from the logs from the Client Sync.
+ * Tracks any timers for users.
+ * Writes the changes to presence state to the logs.
+ * Shards by user ID somehow?
+
+## Client Sync
+
+ * Handle /client/v2/sync requests.
+ * Reads new events and the current state of the rooms from logs written by the Room Server.
+ * Reads new receipts positions from the logs written by the Receipts Server.
+ * Reads changes to presence from the logs written by the Presence Server.
+ * Reads changes to typing from the logs written by the Typing Server.
+ * Writes when a client starts and stops syncing to the logs.
+
+## Client Search
+
+ * Handle whatever the client API path for event search is?
+ * Reads new events and the current state of the rooms from logs writeen by the Room Server.
+ * Maintains a full text search index of somekind.
+
+## Client Push
+
+ * Pushes unread messages to remote push servers.
+ * Reads new events and the current state of the rooms from logs writeen by the Room Server.
+ * Reads the position of the read marker from the Receipts Server.
+ * Makes outbound HTTP hits to the push server for the client device.