diff --git a/app/src/main/java/org/thoughtcrime/securesms/database/PendingPniSignatureMessageTable.kt b/app/src/main/java/org/thoughtcrime/securesms/database/PendingPniSignatureMessageTable.kt
index 06877b573f..080dfc8f08 100644
--- a/app/src/main/java/org/thoughtcrime/securesms/database/PendingPniSignatureMessageTable.kt
+++ b/app/src/main/java/org/thoughtcrime/securesms/database/PendingPniSignatureMessageTable.kt
@@ -8,7 +8,10 @@ import org.signal.core.util.logging.Log
 import org.signal.core.util.update
 import org.signal.core.util.withinTransaction
 import org.thoughtcrime.securesms.recipients.RecipientId
+import org.thoughtcrime.securesms.util.LRUCache
 import org.whispersystems.signalservice.api.messages.SendMessageResult
+import java.util.concurrent.locks.ReentrantReadWriteLock
+import kotlin.concurrent.withLock
 
 /**
  * Contains records of messages that have been sent with PniSignatures on them.
@@ -41,45 +44,71 @@ class PendingPniSignatureMessageTable(context: Context, databaseHelper: SignalDa
     )
   }
 
+  /**
+   * Caches whether or not there are any pending PNI signature messages for a given recipient.
+   * - If there are, there will be an entry with 'true' for that recipient.
+   * - If there aren't, there will be an entry with 'false'.
+   * - If the entry is null, we do not know, and you should check the database.
+   *
+   * This cache exists because this table is hit very frequently via delivery receipt handling.
+   */
+  private val pendingPniSignaturesCache: MutableMap<RecipientId, Boolean?> = LRUCache(1000)
+  private val pendingPniSignaturesCacheLock = ReentrantReadWriteLock()
+
   fun insertIfNecessary(recipientId: RecipientId, sentTimestamp: Long, result: SendMessageResult) {
-    if (!result.isSuccess) {
+    if (!result.isSuccess || result.success.devices.isEmpty()) {
       return
     }
 
-    writableDatabase.withinTransaction { db ->
-      for (deviceId in result.success.devices) {
-        val values = contentValuesOf(
-          RECIPIENT_ID to recipientId.serialize(),
-          SENT_TIMESTAMP to sentTimestamp,
-          DEVICE_ID to deviceId
-        )
+    pendingPniSignaturesCacheLock.writeLock().withLock {
+      writableDatabase.withinTransaction { db ->
+        for (deviceId in result.success.devices) {
+          val values = contentValuesOf(
+            RECIPIENT_ID to recipientId.serialize(),
+            SENT_TIMESTAMP to sentTimestamp,
+            DEVICE_ID to deviceId
+          )
 
-        db.insertWithOnConflict(TABLE_NAME, null, values, SQLiteDatabase.CONFLICT_IGNORE)
+          db.insertWithOnConflict(TABLE_NAME, null, values, SQLiteDatabase.CONFLICT_IGNORE)
+        }
       }
+
+      pendingPniSignaturesCache[recipientId] = true
     }
   }
 
   fun acknowledgeReceipts(recipientId: RecipientId, sentTimestamps: Collection<Long>, deviceId: Int) {
-    writableDatabase.withinTransaction { db ->
-      val count = db
-        .delete(TABLE_NAME)
-        .where("$RECIPIENT_ID = ? AND $SENT_TIMESTAMP IN (?) AND $DEVICE_ID = ?", recipientId, sentTimestamps.joinToString(separator = ","), deviceId)
-        .run()
-
-      if (count <= 0) {
-        return@withinTransaction
+    pendingPniSignaturesCacheLock.readLock().withLock {
+      if (pendingPniSignaturesCache[recipientId] == false) {
+        return
       }
+    }
 
-      val stillPending: Boolean = db.exists(TABLE_NAME).where("$RECIPIENT_ID = ? AND $SENT_TIMESTAMP = ?", recipientId, sentTimestamps).run()
-
-      if (!stillPending) {
-        Log.i(TAG, "All devices for ($recipientId, $sentTimestamps) have acked the PNI signature message. Clearing flag and removing any other pending receipts.")
-        SignalDatabase.recipients.clearNeedsPniSignature(recipientId)
-
-        db
+    pendingPniSignaturesCacheLock.writeLock().withLock {
+      writableDatabase.withinTransaction { db ->
+        val count = db
           .delete(TABLE_NAME)
-          .where("$RECIPIENT_ID = ?", recipientId)
+          .where("$RECIPIENT_ID = ? AND $SENT_TIMESTAMP IN (?) AND $DEVICE_ID = ?", recipientId, sentTimestamps.joinToString(separator = ","), deviceId)
           .run()
+
+        if (count <= 0) {
+          pendingPniSignaturesCache[recipientId] = false
+          return@withinTransaction
+        }
+
+        val stillPending: Boolean = db.exists(TABLE_NAME).where("$RECIPIENT_ID = ? AND $SENT_TIMESTAMP = ?", recipientId, sentTimestamps).run()
+
+        if (!stillPending) {
+          Log.i(TAG, "All devices for ($recipientId, $sentTimestamps) have acked the PNI signature message. Clearing flag and removing any other pending receipts.")
+          SignalDatabase.recipients.clearNeedsPniSignature(recipientId)
+
+          db
+            .delete(TABLE_NAME)
+            .where("$RECIPIENT_ID = ?", recipientId)
+            .run()
+        }
+
+        pendingPniSignaturesCache[recipientId] = stillPending
       }
     }
   }