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diff --git a/src/kernel/mempool_entry.h b/src/kernel/mempool_entry.h
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+// Copyright (c) 2009-2022 The Bitcoin Core developers
+// Distributed under the MIT software license, see the accompanying
+// file COPYING or http://www.opensource.org/licenses/mit-license.php.
+
+#ifndef BITCOIN_KERNEL_MEMPOOL_ENTRY_H
+#define BITCOIN_KERNEL_MEMPOOL_ENTRY_H
+
+#include <consensus/amount.h>
+#include <consensus/validation.h>
+#include <core_memusage.h>
+#include <policy/policy.h>
+#include <policy/settings.h>
+#include <primitives/transaction.h>
+#include <util/epochguard.h>
+#include <util/overflow.h>
+
+#include <chrono>
+#include <functional>
+#include <memory>
+#include <set>
+#include <stddef.h>
+#include <stdint.h>
+
+class CBlockIndex;
+
+struct LockPoints {
+    // Will be set to the blockchain height and median time past
+    // values that would be necessary to satisfy all relative locktime
+    // constraints (BIP68) of this tx given our view of block chain history
+    int height{0};
+    int64_t time{0};
+    // As long as the current chain descends from the highest height block
+    // containing one of the inputs used in the calculation, then the cached
+    // values are still valid even after a reorg.
+    CBlockIndex* maxInputBlock{nullptr};
+};
+
+struct CompareIteratorByHash {
+    // SFINAE for T where T is either a pointer type (e.g., a txiter) or a reference_wrapper<T>
+    // (e.g. a wrapped CTxMemPoolEntry&)
+    template <typename T>
+    bool operator()(const std::reference_wrapper<T>& a, const std::reference_wrapper<T>& b) const
+    {
+        return a.get().GetTx().GetHash() < b.get().GetTx().GetHash();
+    }
+    template <typename T>
+    bool operator()(const T& a, const T& b) const
+    {
+        return a->GetTx().GetHash() < b->GetTx().GetHash();
+    }
+};
+
+/** \class CTxMemPoolEntry
+ *
+ * CTxMemPoolEntry stores data about the corresponding transaction, as well
+ * as data about all in-mempool transactions that depend on the transaction
+ * ("descendant" transactions).
+ *
+ * When a new entry is added to the mempool, we update the descendant state
+ * (nCountWithDescendants, nSizeWithDescendants, and nModFeesWithDescendants) for
+ * all ancestors of the newly added transaction.
+ *
+ */
+
+class CTxMemPoolEntry
+{
+public:
+    typedef std::reference_wrapper<const CTxMemPoolEntry> CTxMemPoolEntryRef;
+    // two aliases, should the types ever diverge
+    typedef std::set<CTxMemPoolEntryRef, CompareIteratorByHash> Parents;
+    typedef std::set<CTxMemPoolEntryRef, CompareIteratorByHash> Children;
+
+private:
+    const CTransactionRef tx;
+    mutable Parents m_parents;
+    mutable Children m_children;
+    const CAmount nFee;             //!< Cached to avoid expensive parent-transaction lookups
+    const size_t nTxWeight;         //!< ... and avoid recomputing tx weight (also used for GetTxSize())
+    const size_t nUsageSize;        //!< ... and total memory usage
+    const int64_t nTime;            //!< Local time when entering the mempool
+    const unsigned int entryHeight; //!< Chain height when entering the mempool
+    const bool spendsCoinbase;      //!< keep track of transactions that spend a coinbase
+    const int64_t sigOpCost;        //!< Total sigop cost
+    CAmount m_modified_fee;         //!< Used for determining the priority of the transaction for mining in a block
+    LockPoints lockPoints;          //!< Track the height and time at which tx was final
+
+    // Information about descendants of this transaction that are in the
+    // mempool; if we remove this transaction we must remove all of these
+    // descendants as well.
+    uint64_t nCountWithDescendants{1}; //!< number of descendant transactions
+    uint64_t nSizeWithDescendants;     //!< ... and size
+    CAmount nModFeesWithDescendants;   //!< ... and total fees (all including us)
+
+    // Analogous statistics for ancestor transactions
+    uint64_t nCountWithAncestors{1};
+    uint64_t nSizeWithAncestors;
+    CAmount nModFeesWithAncestors;
+    int64_t nSigOpCostWithAncestors;
+
+public:
+    CTxMemPoolEntry(const CTransactionRef& tx, CAmount fee,
+                    int64_t time, unsigned int entry_height,
+                    bool spends_coinbase,
+                    int64_t sigops_cost, LockPoints lp)
+        : tx{tx},
+          nFee{fee},
+          nTxWeight(GetTransactionWeight(*tx)),
+          nUsageSize{RecursiveDynamicUsage(tx)},
+          nTime{time},
+          entryHeight{entry_height},
+          spendsCoinbase{spends_coinbase},
+          sigOpCost{sigops_cost},
+          m_modified_fee{nFee},
+          lockPoints{lp},
+          nSizeWithDescendants{GetTxSize()},
+          nModFeesWithDescendants{nFee},
+          nSizeWithAncestors{GetTxSize()},
+          nModFeesWithAncestors{nFee},
+          nSigOpCostWithAncestors{sigOpCost} {}
+
+    const CTransaction& GetTx() const { return *this->tx; }
+    CTransactionRef GetSharedTx() const { return this->tx; }
+    const CAmount& GetFee() const { return nFee; }
+    size_t GetTxSize() const
+    {
+        return GetVirtualTransactionSize(nTxWeight, sigOpCost, ::nBytesPerSigOp);
+    }
+    size_t GetTxWeight() const { return nTxWeight; }
+    std::chrono::seconds GetTime() const { return std::chrono::seconds{nTime}; }
+    unsigned int GetHeight() const { return entryHeight; }
+    int64_t GetSigOpCost() const { return sigOpCost; }
+    CAmount GetModifiedFee() const { return m_modified_fee; }
+    size_t DynamicMemoryUsage() const { return nUsageSize; }
+    const LockPoints& GetLockPoints() const { return lockPoints; }
+
+    // Adjusts the descendant state.
+    void UpdateDescendantState(int64_t modifySize, CAmount modifyFee, int64_t modifyCount);
+    // Adjusts the ancestor state
+    void UpdateAncestorState(int64_t modifySize, CAmount modifyFee, int64_t modifyCount, int64_t modifySigOps);
+    // Updates the modified fees with descendants/ancestors.
+    void UpdateModifiedFee(CAmount fee_diff)
+    {
+        nModFeesWithDescendants = SaturatingAdd(nModFeesWithDescendants, fee_diff);
+        nModFeesWithAncestors = SaturatingAdd(nModFeesWithAncestors, fee_diff);
+        m_modified_fee = SaturatingAdd(m_modified_fee, fee_diff);
+    }
+
+    // Update the LockPoints after a reorg
+    void UpdateLockPoints(const LockPoints& lp)
+    {
+        lockPoints = lp;
+    }
+
+    uint64_t GetCountWithDescendants() const { return nCountWithDescendants; }
+    uint64_t GetSizeWithDescendants() const { return nSizeWithDescendants; }
+    CAmount GetModFeesWithDescendants() const { return nModFeesWithDescendants; }
+
+    bool GetSpendsCoinbase() const { return spendsCoinbase; }
+
+    uint64_t GetCountWithAncestors() const { return nCountWithAncestors; }
+    uint64_t GetSizeWithAncestors() const { return nSizeWithAncestors; }
+    CAmount GetModFeesWithAncestors() const { return nModFeesWithAncestors; }
+    int64_t GetSigOpCostWithAncestors() const { return nSigOpCostWithAncestors; }
+
+    const Parents& GetMemPoolParentsConst() const { return m_parents; }
+    const Children& GetMemPoolChildrenConst() const { return m_children; }
+    Parents& GetMemPoolParents() const { return m_parents; }
+    Children& GetMemPoolChildren() const { return m_children; }
+
+    mutable size_t vTxHashesIdx; //!< Index in mempool's vTxHashes
+    mutable Epoch::Marker m_epoch_marker; //!< epoch when last touched, useful for graph algorithms
+};
+
+#endif // BITCOIN_KERNEL_MEMPOOL_ENTRY_H