diff --git a/migrations/1703177555075_mempool-digest-table.js b/migrations/1703177555075_mempool-digest-table.js
new file mode 100644
index 0000000000..af0185ac74
--- /dev/null
+++ b/migrations/1703177555075_mempool-digest-table.js
@@ -0,0 +1,27 @@
+/* eslint-disable camelcase */
+
+exports.shorthands = undefined;
+
+exports.up = pgm => {
+  pgm.addColumn('chain_tip', {
+    mempool_tx_count: {
+      type: 'int',
+      default: 0,
+    },
+    mempool_updated_at: {
+      type: 'timestamptz',
+      default: pgm.func('(NOW())'),
+    },
+  });
+  pgm.sql(`
+    UPDATE chain_tip SET
+      mempool_tx_count = (SELECT COUNT(*)::int FROM mempool_txs WHERE pruned = FALSE),
+      mempool_updated_at = NOW()
+  `);
+  pgm.alterColumn('chain_tip', 'mempool_tx_count', { notNull: true });
+  pgm.alterColumn('chain_tip', 'mempool_updated_at', { notNull: true });
+};
+
+exports.down = pgm => {
+  pgm.dropColumn('chain_tip', ['mempool_tx_count', 'mempool_updated_at']);
+};
diff --git a/src/datastore/pg-store.ts b/src/datastore/pg-store.ts
index e33acd8651..88d1776816 100644
--- a/src/datastore/pg-store.ts
+++ b/src/datastore/pg-store.ts
@@ -1306,12 +1306,13 @@ export class PgStore {
       const unanchoredTxs: string[] = !includeUnanchored
         ? (await this.getUnanchoredTxsInternal(sql)).txs.map(tx => tx.tx_id)
         : [];
+      // If caller is not filtering by any param, get the tx count from the `chain_tip` table.
+      const count =
+        senderAddress || recipientAddress || address
+          ? sql`(COUNT(*) OVER())::int AS count`
+          : sql`(SELECT mempool_tx_count FROM chain_tip) AS count`;
       const resultQuery = await sql<(MempoolTxQueryResult & { count: number })[]>`
-        SELECT ${unsafeCols(sql, [
-          ...MEMPOOL_TX_COLUMNS,
-          abiColumn('mempool_txs'),
-          '(COUNT(*) OVER())::INTEGER AS count',
-        ])}
+        SELECT ${unsafeCols(sql, [...MEMPOOL_TX_COLUMNS, abiColumn('mempool_txs')])}, ${count}
         FROM mempool_txs
         WHERE ${
           address
@@ -1355,7 +1356,9 @@ export class PgStore {
    * @returns `FoundOrNot` object with a possible `digest` string.
    */
   async getMempoolTxDigest(): Promise<FoundOrNot<{ digest: string }>> {
-    const result = await this.sql<{ digest: string }[]>`SELECT digest FROM mempool_digest`;
+    const result = await this.sql<{ digest: string }[]>`
+      SELECT date_part('epoch', mempool_updated_at)::text AS digest FROM chain_tip
+    `;
     if (result.length === 0) {
       return { found: false } as const;
     }
diff --git a/src/datastore/pg-write-store.ts b/src/datastore/pg-write-store.ts
index f2224c99c9..55e9ca48a5 100644
--- a/src/datastore/pg-write-store.ts
+++ b/src/datastore/pg-write-store.ts
@@ -705,8 +705,6 @@ export class PgWriteStore extends PgStore {
         `;
     });
 
-    await this.refreshMaterializedView('mempool_digest');
-
     if (this.notifier) {
       for (const microblock of dbMicroblocks) {
         await this.notifier.sendMicroblock({ microblockHash: microblock.microblock_hash });
@@ -736,20 +734,28 @@ export class PgWriteStore extends PgStore {
   // NOTE: this is essentially a work-around for whatever bug is causing the underlying problem.
   async reconcileMempoolStatus(sql: PgSqlClient): Promise<void> {
     const txsResult = await sql<{ tx_id: string }[]>`
-      UPDATE mempool_txs
-      SET pruned = true
-      FROM txs
-      WHERE
-        mempool_txs.tx_id = txs.tx_id AND
-        mempool_txs.pruned = false AND
-        txs.canonical = true AND
-        txs.microblock_canonical = true AND
-        txs.status IN ${sql([
-          DbTxStatus.Success,
-          DbTxStatus.AbortByResponse,
-          DbTxStatus.AbortByPostCondition,
-        ])}
-      RETURNING mempool_txs.tx_id
+      WITH pruned AS (
+        UPDATE mempool_txs
+        SET pruned = true
+        FROM txs
+        WHERE
+          mempool_txs.tx_id = txs.tx_id AND
+          mempool_txs.pruned = false AND
+          txs.canonical = true AND
+          txs.microblock_canonical = true AND
+          txs.status IN ${sql([
+            DbTxStatus.Success,
+            DbTxStatus.AbortByResponse,
+            DbTxStatus.AbortByPostCondition,
+          ])}
+        RETURNING mempool_txs.tx_id
+      ),
+      count_update AS (
+        UPDATE chain_tip SET
+          mempool_tx_count = mempool_tx_count - (SELECT COUNT(*) FROM pruned),
+          mempool_updated_at = NOW()
+      )
+      SELECT tx_id FROM pruned
     `;
     if (txsResult.length > 0) {
       const txs = txsResult.map(tx => tx.tx_id);
@@ -1656,89 +1662,95 @@ export class PgWriteStore extends PgStore {
     return result.count;
   }
 
-  async insertDbMempoolTx(
-    tx: DbMempoolTxRaw,
+  async insertDbMempoolTxs(
+    txs: DbMempoolTxRaw[],
     chainTip: DbChainTip,
     sql: PgSqlClient
-  ): Promise<boolean> {
-    const values: MempoolTxInsertValues = {
-      pruned: tx.pruned,
-      tx_id: tx.tx_id,
-      raw_tx: tx.raw_tx,
-      type_id: tx.type_id,
-      anchor_mode: tx.anchor_mode,
-      status: tx.status,
-      receipt_time: tx.receipt_time,
-      receipt_block_height: chainTip.block_height,
-      post_conditions: tx.post_conditions,
-      nonce: tx.nonce,
-      fee_rate: tx.fee_rate,
-      sponsored: tx.sponsored,
-      sponsor_nonce: tx.sponsor_nonce ?? null,
-      sponsor_address: tx.sponsor_address ?? null,
-      sender_address: tx.sender_address,
-      origin_hash_mode: tx.origin_hash_mode,
-      token_transfer_recipient_address: tx.token_transfer_recipient_address ?? null,
-      token_transfer_amount: tx.token_transfer_amount ?? null,
-      token_transfer_memo: tx.token_transfer_memo ?? null,
-      smart_contract_clarity_version: tx.smart_contract_clarity_version ?? null,
-      smart_contract_contract_id: tx.smart_contract_contract_id ?? null,
-      smart_contract_source_code: tx.smart_contract_source_code ?? null,
-      contract_call_contract_id: tx.contract_call_contract_id ?? null,
-      contract_call_function_name: tx.contract_call_function_name ?? null,
-      contract_call_function_args: tx.contract_call_function_args ?? null,
-      poison_microblock_header_1: tx.poison_microblock_header_1 ?? null,
-      poison_microblock_header_2: tx.poison_microblock_header_2 ?? null,
-      coinbase_payload: tx.coinbase_payload ?? null,
-      coinbase_alt_recipient: tx.coinbase_alt_recipient ?? null,
-    };
-    const result = await sql`
-      INSERT INTO mempool_txs ${sql(values)}
-      ON CONFLICT ON CONSTRAINT unique_tx_id DO NOTHING
-    `;
-    if (result.count !== 1) {
-      const errMsg = `A duplicate transaction was attempted to be inserted into the mempool_txs table: ${tx.tx_id}`;
-      logger.warn(errMsg);
-      return false;
-    } else {
-      return true;
+  ): Promise<string[]> {
+    const txIds: string[] = [];
+    for (const batch of batchIterate(txs, 500)) {
+      const values: MempoolTxInsertValues[] = batch.map(tx => ({
+        pruned: tx.pruned,
+        tx_id: tx.tx_id,
+        raw_tx: tx.raw_tx,
+        type_id: tx.type_id,
+        anchor_mode: tx.anchor_mode,
+        status: tx.status,
+        receipt_time: tx.receipt_time,
+        receipt_block_height: chainTip.block_height,
+        post_conditions: tx.post_conditions,
+        nonce: tx.nonce,
+        fee_rate: tx.fee_rate,
+        sponsored: tx.sponsored,
+        sponsor_nonce: tx.sponsor_nonce ?? null,
+        sponsor_address: tx.sponsor_address ?? null,
+        sender_address: tx.sender_address,
+        origin_hash_mode: tx.origin_hash_mode,
+        token_transfer_recipient_address: tx.token_transfer_recipient_address ?? null,
+        token_transfer_amount: tx.token_transfer_amount ?? null,
+        token_transfer_memo: tx.token_transfer_memo ?? null,
+        smart_contract_clarity_version: tx.smart_contract_clarity_version ?? null,
+        smart_contract_contract_id: tx.smart_contract_contract_id ?? null,
+        smart_contract_source_code: tx.smart_contract_source_code ?? null,
+        contract_call_contract_id: tx.contract_call_contract_id ?? null,
+        contract_call_function_name: tx.contract_call_function_name ?? null,
+        contract_call_function_args: tx.contract_call_function_args ?? null,
+        poison_microblock_header_1: tx.poison_microblock_header_1 ?? null,
+        poison_microblock_header_2: tx.poison_microblock_header_2 ?? null,
+        coinbase_payload: tx.coinbase_payload ?? null,
+        coinbase_alt_recipient: tx.coinbase_alt_recipient ?? null,
+      }));
+      const result = await sql<{ tx_id: string }[]>`
+        WITH inserted AS (
+          INSERT INTO mempool_txs ${sql(values)}
+          ON CONFLICT ON CONSTRAINT unique_tx_id DO NOTHING
+          RETURNING tx_id
+        ),
+        count_update AS (
+          UPDATE chain_tip SET
+            mempool_tx_count = mempool_tx_count + (SELECT COUNT(*) FROM inserted),
+            mempool_updated_at = NOW()
+        )
+        SELECT tx_id FROM inserted
+      `;
+      txIds.push(...result.map(r => r.tx_id));
     }
+    return txIds;
   }
 
   async updateMempoolTxs({ mempoolTxs: txs }: { mempoolTxs: DbMempoolTxRaw[] }): Promise<void> {
     const updatedTxIds: string[] = [];
     await this.sqlWriteTransaction(async sql => {
       const chainTip = await this.getChainTip();
-      for (const tx of txs) {
-        const inserted = await this.insertDbMempoolTx(tx, chainTip, sql);
-        if (inserted) {
-          updatedTxIds.push(tx.tx_id);
-        }
-      }
+      updatedTxIds.push(...(await this.insertDbMempoolTxs(txs, chainTip, sql)));
       if (!this.isEventReplay) {
         await this.reconcileMempoolStatus(sql);
-
         const mempoolStats = await this.getMempoolStatsInternal({ sql });
         this.eventEmitter.emit('mempoolStatsUpdate', mempoolStats);
       }
     });
-    await this.refreshMaterializedView('mempool_digest');
     for (const txId of updatedTxIds) {
-      await this.notifier?.sendTx({ txId: txId });
+      await this.notifier?.sendTx({ txId });
     }
   }
 
   async dropMempoolTxs({ status, txIds }: { status: DbTxStatus; txIds: string[] }): Promise<void> {
-    const updateResults = await this.sql<MempoolTxQueryResult[]>`
-      UPDATE mempool_txs
-      SET pruned = true, status = ${status}
-      WHERE tx_id IN ${this.sql(txIds)}
-      RETURNING ${this.sql(MEMPOOL_TX_COLUMNS)}
+    const updateResults = await this.sql<{ tx_id: string }[]>`
+      WITH pruned AS (
+        UPDATE mempool_txs
+        SET pruned = TRUE, status = ${status}
+        WHERE tx_id IN ${this.sql(txIds)} AND pruned = FALSE
+        RETURNING tx_id
+      ),
+      count_update AS (
+        UPDATE chain_tip SET
+          mempool_tx_count = mempool_tx_count - (SELECT COUNT(*) FROM pruned),
+          mempool_updated_at = NOW()
+      )
+      SELECT tx_id FROM pruned
     `;
-    const updatedTxs = updateResults.map(r => parseMempoolTxQueryResult(r));
-    await this.refreshMaterializedView('mempool_digest');
-    for (const tx of updatedTxs) {
-      await this.notifier?.sendTx({ txId: tx.tx_id });
+    for (const txId of updateResults.map(r => r.tx_id)) {
+      await this.notifier?.sendTx({ txId });
     }
   }
 
@@ -2326,19 +2338,24 @@ export class PgWriteStore extends PgStore {
    * @param txIds - List of transactions to update in the mempool
    */
   async restoreMempoolTxs(sql: PgSqlClient, txIds: string[]): Promise<{ restoredTxs: string[] }> {
-    if (txIds.length === 0) {
-      // Avoid an unnecessary query.
-      return { restoredTxs: [] };
-    }
+    if (txIds.length === 0) return { restoredTxs: [] };
     for (const txId of txIds) {
       logger.debug(`Restoring mempool tx: ${txId}`);
     }
 
     const updatedRows = await sql<{ tx_id: string }[]>`
-      UPDATE mempool_txs
-      SET pruned = false
-      WHERE tx_id IN ${sql(txIds)}
-      RETURNING tx_id
+      WITH restored AS (
+        UPDATE mempool_txs
+        SET pruned = FALSE
+        WHERE tx_id IN ${sql(txIds)} AND pruned = TRUE
+        RETURNING tx_id
+      ),
+      count_update AS (
+        UPDATE chain_tip SET
+          mempool_tx_count = mempool_tx_count + (SELECT COUNT(*) FROM restored),
+          mempool_updated_at = NOW()
+      )
+      SELECT tx_id FROM restored
     `;
 
     const updatedTxs = updatedRows.map(r => r.tx_id);
@@ -2393,13 +2410,20 @@ export class PgWriteStore extends PgStore {
       logger.debug(`Pruning mempool tx: ${txId}`);
     }
     const updateResults = await sql<{ tx_id: string }[]>`
-      UPDATE mempool_txs
-      SET pruned = true
-      WHERE tx_id IN ${sql(txIds)}
-      RETURNING tx_id
+      WITH pruned AS (
+        UPDATE mempool_txs
+        SET pruned = true
+        WHERE tx_id IN ${sql(txIds)} AND pruned = FALSE
+        RETURNING tx_id
+      ),
+      count_update AS (
+        UPDATE chain_tip SET
+          mempool_tx_count = mempool_tx_count - (SELECT COUNT(*) FROM pruned),
+          mempool_updated_at = NOW()
+      )
+      SELECT tx_id FROM pruned
     `;
-    const removedTxs = updateResults.map(r => r.tx_id);
-    return { removedTxs: removedTxs };
+    return { removedTxs: updateResults.map(r => r.tx_id) };
   }
 
   /**
@@ -2408,27 +2432,26 @@ export class PgWriteStore extends PgStore {
    * @returns List of deleted `tx_id`s
    */
   async deleteGarbageCollectedMempoolTxs(sql: PgSqlClient): Promise<{ deletedTxs: string[] }> {
-    // Get threshold block.
-    const blockThreshold = process.env['STACKS_MEMPOOL_TX_GARBAGE_COLLECTION_THRESHOLD'] ?? 256;
-    const cutoffResults = await sql<{ block_height: number }[]>`
-      SELECT (MAX(block_height) - ${blockThreshold}) AS block_height
-      FROM blocks
-      WHERE canonical = TRUE
-    `;
-    if (cutoffResults.length != 1) {
-      return { deletedTxs: [] };
-    }
-    const cutoffBlockHeight = cutoffResults[0].block_height;
-    // Delete every mempool tx that came before that block.
+    const blockThreshold = parseInt(
+      process.env['STACKS_MEMPOOL_TX_GARBAGE_COLLECTION_THRESHOLD'] ?? '256'
+    );
     // TODO: Use DELETE instead of UPDATE once we implement a non-archival API replay mode.
     const deletedTxResults = await sql<{ tx_id: string }[]>`
-      UPDATE mempool_txs
-      SET pruned = TRUE, status = ${DbTxStatus.DroppedApiGarbageCollect}
-      WHERE pruned = FALSE AND receipt_block_height < ${cutoffBlockHeight}
-      RETURNING tx_id
+      WITH pruned AS (
+        UPDATE mempool_txs
+        SET pruned = TRUE, status = ${DbTxStatus.DroppedApiGarbageCollect}
+        WHERE pruned = FALSE
+          AND receipt_block_height <= (SELECT block_height - ${blockThreshold} FROM chain_tip)
+        RETURNING tx_id
+      ),
+      count_update AS (
+        UPDATE chain_tip SET
+          mempool_tx_count = mempool_tx_count - (SELECT COUNT(*) FROM pruned),
+          mempool_updated_at = NOW()
+      )
+      SELECT tx_id FROM pruned
     `;
-    const deletedTxs = deletedTxResults.map(r => r.tx_id);
-    return { deletedTxs: deletedTxs };
+    return { deletedTxs: deletedTxResults.map(r => r.tx_id) };
   }
 
   async markEntitiesCanonical(
diff --git a/src/event-replay/event-replay.ts b/src/event-replay/event-replay.ts
index 53cb077509..172c13e5d1 100644
--- a/src/event-replay/event-replay.ts
+++ b/src/event-replay/event-replay.ts
@@ -167,7 +167,6 @@ export async function importEventsFromTsv(
       responses.push(response);
     }
   }
-  await db.finishEventReplay();
   console.log(`Event import and playback successful.`);
   await eventServer.closeAsync();
   await db.close();
diff --git a/src/tests/cache-control-tests.ts b/src/tests/cache-control-tests.ts
index 0718f0574b..a2d88c960d 100644
--- a/src/tests/cache-control-tests.ts
+++ b/src/tests/cache-control-tests.ts
@@ -373,7 +373,7 @@ describe('cache-control tests', () => {
     const request1 = await supertest(api.server).get('/extended/v1/tx/mempool');
     expect(request1.status).toBe(200);
     expect(request1.type).toBe('application/json');
-    expect(request1.headers['etag']).toEqual('"0"');
+    const etag0 = request1.headers['etag'];
 
     // Add mempool txs.
     const mempoolTx1 = testMempoolTx({ tx_id: '0x1101' });
@@ -386,6 +386,7 @@ describe('cache-control tests', () => {
     expect(request2.type).toBe('application/json');
     expect(request2.headers['etag']).toBeTruthy();
     const etag1 = request2.headers['etag'];
+    expect(etag1).not.toEqual(etag0);
 
     // Cache works with valid ETag.
     const request3 = await supertest(api.server)
@@ -416,13 +417,12 @@ describe('cache-control tests', () => {
       .build();
     await db.update(block2);
 
-    // Cache is now a miss and ETag is zero because mempool is empty.
+    // Cache is now a miss.
     const request5 = await supertest(api.server)
       .get('/extended/v1/tx/mempool')
       .set('If-None-Match', etag2);
     expect(request5.status).toBe(200);
     expect(request5.type).toBe('application/json');
-    expect(request5.headers['etag']).toEqual('"0"');
     const etag3 = request5.headers['etag'];
 
     // Restore a tx back into the mempool by making its anchor block non-canonical.
@@ -449,7 +449,7 @@ describe('cache-control tests', () => {
       .set('If-None-Match', etag3);
     expect(request6.status).toBe(200);
     expect(request6.type).toBe('application/json');
-    expect(request6.headers['etag']).toEqual(etag2);
+    expect(request6.headers['etag']).not.toEqual(etag3);
     const etag4 = request6.headers['etag'];
 
     // Garbage collect all txs.
@@ -463,25 +463,13 @@ describe('cache-control tests', () => {
       .build();
     await db.update(block4);
 
-    // ETag zero once again.
+    // ETag changes once again.
     const request7 = await supertest(api.server)
       .get('/extended/v1/tx/mempool')
       .set('If-None-Match', etag4);
     expect(request7.status).toBe(200);
     expect(request7.type).toBe('application/json');
-    expect(request7.headers['etag']).toEqual('"0"');
-
-    // Simulate an incompatible pg version (without `bit_xor`).
-    await client.begin(async sql => {
-      await sql`DROP MATERIALIZED VIEW mempool_digest`;
-      await sql`CREATE MATERIALIZED VIEW mempool_digest AS (SELECT NULL AS digest)`;
-    });
-
-    // ETag is undefined as if mempool cache did not exist.
-    const request8 = await supertest(api.server).get('/extended/v1/tx/mempool');
-    expect(request8.status).toBe(200);
-    expect(request8.type).toBe('application/json');
-    expect(request8.headers['etag']).toBeUndefined();
+    expect(request7.headers['etag']).not.toEqual(etag4);
   });
 
   test('transaction cache control', async () => {
diff --git a/src/tests/mempool-tests.ts b/src/tests/mempool-tests.ts
index b31952e829..b44440fae4 100644
--- a/src/tests/mempool-tests.ts
+++ b/src/tests/mempool-tests.ts
@@ -1489,7 +1489,7 @@ describe('mempool tests', () => {
     // directly inserting the mempool-tx and mined-tx, bypassing the normal update functions.
     await db.updateBlock(db.sql, dbBlock1);
     const chainTip = await db.getChainTip();
-    await db.insertDbMempoolTx(mempoolTx, chainTip, db.sql);
+    await db.insertDbMempoolTxs([mempoolTx], chainTip, db.sql);
     await db.updateTx(db.sql, dbTx1);
 
     // Verify tx shows up in mempool (non-pruned)
@@ -1497,6 +1497,8 @@ describe('mempool tests', () => {
       `/extended/v1/address/${mempoolTx.sender_address}/mempool`
     );
     expect(mempoolResult1.body.results[0].tx_id).toBe(txId);
+    const mempoolCount1 = await supertest(api.server).get(`/extended/v1/tx/mempool`);
+    expect(mempoolCount1.body.total).toBe(1);
     const mempoolResult2 = await supertest(api.server).get(
       `/extended/v1/tx/mempool?sender_address=${senderAddress}`
     );
@@ -1519,6 +1521,8 @@ describe('mempool tests', () => {
       `/extended/v1/address/${mempoolTx.sender_address}/mempool`
     );
     expect(mempoolResult3.body.results).toHaveLength(0);
+    const mempoolCount2 = await supertest(api.server).get(`/extended/v1/tx/mempool`);
+    expect(mempoolCount2.body.total).toBe(0);
     const mempoolResult4 = await supertest(api.server).get(
       `/extended/v1/tx/mempool?sender_address=${senderAddress}`
     );