diff --git a/service/src/main/java/org/whispersystems/textsecuregcm/storage/MessagesCache.java b/service/src/main/java/org/whispersystems/textsecuregcm/storage/MessagesCache.java
index 7db90e492..75eb6346b 100644
--- a/service/src/main/java/org/whispersystems/textsecuregcm/storage/MessagesCache.java
+++ b/service/src/main/java/org/whispersystems/textsecuregcm/storage/MessagesCache.java
@@ -211,10 +211,13 @@ public class MessagesCache {
     this.removeRecipientViewFromMrmDataScript = removeRecipientViewFromMrmDataScript;
   }
 
-  public long insert(final UUID guid, final UUID destinationUuid, final byte destinationDevice,
+  public void insert(final UUID messageGuid,
+      final UUID destinationAccountIdentifier,
+      final byte destinationDeviceId,
       final MessageProtos.Envelope message) {
-    final MessageProtos.Envelope messageWithGuid = message.toBuilder().setServerGuid(guid.toString()).build();
-    return insertTimer.record(() -> insertScript.execute(destinationUuid, destinationDevice, messageWithGuid));
+
+    final MessageProtos.Envelope messageWithGuid = message.toBuilder().setServerGuid(messageGuid.toString()).build();
+    insertTimer.record(() -> insertScript.execute(destinationAccountIdentifier, destinationDeviceId, messageWithGuid));
   }
 
   public byte[] insertSharedMultiRecipientMessagePayload(
diff --git a/service/src/main/java/org/whispersystems/textsecuregcm/storage/MessagesCacheInsertScript.java b/service/src/main/java/org/whispersystems/textsecuregcm/storage/MessagesCacheInsertScript.java
index 87e3ba664..249ba5d78 100644
--- a/service/src/main/java/org/whispersystems/textsecuregcm/storage/MessagesCacheInsertScript.java
+++ b/service/src/main/java/org/whispersystems/textsecuregcm/storage/MessagesCacheInsertScript.java
@@ -27,7 +27,7 @@ class MessagesCacheInsertScript {
     this.insertScript = ClusterLuaScript.fromResource(redisCluster, "lua/insert_item.lua", ScriptOutputType.INTEGER);
   }
 
-  long execute(final UUID destinationUuid, final byte destinationDevice, final MessageProtos.Envelope envelope) {
+  void execute(final UUID destinationUuid, final byte destinationDevice, final MessageProtos.Envelope envelope) {
     assert envelope.hasServerGuid();
     assert envelope.hasServerTimestamp();
 
@@ -43,6 +43,6 @@ class MessagesCacheInsertScript {
         envelope.getServerGuid().getBytes(StandardCharsets.UTF_8) // guid
     ));
 
-    return (long) insertScript.executeBinary(keys, args);
+    insertScript.executeBinary(keys, args);
   }
 }
diff --git a/service/src/test/java/org/whispersystems/textsecuregcm/storage/MessagesCacheInsertScriptTest.java b/service/src/test/java/org/whispersystems/textsecuregcm/storage/MessagesCacheInsertScriptTest.java
index febe8c32e..b43c681a1 100644
--- a/service/src/test/java/org/whispersystems/textsecuregcm/storage/MessagesCacheInsertScriptTest.java
+++ b/service/src/test/java/org/whispersystems/textsecuregcm/storage/MessagesCacheInsertScriptTest.java
@@ -7,8 +7,14 @@ package org.whispersystems.textsecuregcm.storage;
 
 import static org.junit.jupiter.api.Assertions.assertEquals;
 
+import java.io.IOException;
+import java.io.UncheckedIOException;
 import java.time.Instant;
+import java.util.ArrayList;
+import java.util.Collections;
+import java.util.List;
 import java.util.UUID;
+import com.google.protobuf.InvalidProtocolBufferException;
 import org.junit.jupiter.api.Test;
 import org.junit.jupiter.api.extension.RegisterExtension;
 import org.whispersystems.textsecuregcm.entities.MessageProtos;
@@ -21,8 +27,8 @@ class MessagesCacheInsertScriptTest {
 
   @Test
   void testCacheInsertScript() throws Exception {
-    final MessagesCacheInsertScript insertScript = new MessagesCacheInsertScript(
-        REDIS_CLUSTER_EXTENSION.getRedisCluster());
+    final MessagesCacheInsertScript insertScript =
+        new MessagesCacheInsertScript(REDIS_CLUSTER_EXTENSION.getRedisCluster());
 
     final UUID destinationUuid = UUID.randomUUID();
     final byte deviceId = 1;
@@ -31,15 +37,43 @@ class MessagesCacheInsertScriptTest {
         .setServerGuid(UUID.randomUUID().toString())
         .build();
 
-    assertEquals(1, insertScript.execute(destinationUuid, deviceId, envelope1));
+    insertScript.execute(destinationUuid, deviceId, envelope1);
+
+    assertEquals(List.of(envelope1), getStoredMessages(destinationUuid, deviceId));
 
     final MessageProtos.Envelope envelope2 = MessageProtos.Envelope.newBuilder()
         .setServerTimestamp(Instant.now().getEpochSecond())
         .setServerGuid(UUID.randomUUID().toString())
         .build();
-    assertEquals(2, insertScript.execute(destinationUuid, deviceId, envelope2));
 
-    assertEquals(1, insertScript.execute(destinationUuid, deviceId, envelope1),
-        "Repeated with same guid should have same message ID");
+    insertScript.execute(destinationUuid, deviceId, envelope2);
+
+    assertEquals(List.of(envelope1, envelope2), getStoredMessages(destinationUuid, deviceId));
+
+    insertScript.execute(destinationUuid, deviceId, envelope1);
+
+    assertEquals(List.of(envelope1, envelope2), getStoredMessages(destinationUuid, deviceId),
+        "Messages with same GUID should be deduplicated");
+  }
+
+  private List<MessageProtos.Envelope> getStoredMessages(final UUID destinationUuid, final byte deviceId) throws IOException {
+    final MessagesCacheGetItemsScript getItemsScript =
+        new MessagesCacheGetItemsScript(REDIS_CLUSTER_EXTENSION.getRedisCluster());
+
+    final List<byte[]> queueItems = getItemsScript.execute(destinationUuid, deviceId, 1024, 0)
+        .blockOptional()
+        .orElseGet(Collections::emptyList);
+
+    final List<MessageProtos.Envelope> messages = new ArrayList<>(queueItems.size() / 2);
+
+    for (int i = 0; i < queueItems.size(); i += 2) {
+      try {
+        messages.add(MessageProtos.Envelope.parseFrom(queueItems.get(i)));
+      } catch (final InvalidProtocolBufferException e) {
+        throw new UncheckedIOException(e);
+      }
+    }
+
+    return messages;
   }
 }
diff --git a/service/src/test/java/org/whispersystems/textsecuregcm/storage/MessagesCacheTest.java b/service/src/test/java/org/whispersystems/textsecuregcm/storage/MessagesCacheTest.java
index 299898323..d5d1817ed 100644
--- a/service/src/test/java/org/whispersystems/textsecuregcm/storage/MessagesCacheTest.java
+++ b/service/src/test/java/org/whispersystems/textsecuregcm/storage/MessagesCacheTest.java
@@ -6,6 +6,7 @@
 package org.whispersystems.textsecuregcm.storage;
 
 import static org.junit.jupiter.api.Assertions.assertArrayEquals;
+import static org.junit.jupiter.api.Assertions.assertDoesNotThrow;
 import static org.junit.jupiter.api.Assertions.assertEquals;
 import static org.junit.jupiter.api.Assertions.assertFalse;
 import static org.junit.jupiter.api.Assertions.assertTimeoutPreemptively;
@@ -132,8 +133,8 @@ class MessagesCacheTest {
     @ValueSource(booleans = {true, false})
     void testInsert(final boolean sealedSender) {
       final UUID messageGuid = UUID.randomUUID();
-      assertTrue(messagesCache.insert(messageGuid, DESTINATION_UUID, DESTINATION_DEVICE_ID,
-          generateRandomMessage(messageGuid, sealedSender)) > 0);
+      assertDoesNotThrow(() -> messagesCache.insert(messageGuid, DESTINATION_UUID, DESTINATION_DEVICE_ID,
+          generateRandomMessage(messageGuid, sealedSender)));
     }
 
     @Test
@@ -141,12 +142,13 @@ class MessagesCacheTest {
       final UUID duplicateGuid = UUID.randomUUID();
       final MessageProtos.Envelope duplicateMessage = generateRandomMessage(duplicateGuid, false);
 
-      final long firstId = messagesCache.insert(duplicateGuid, DESTINATION_UUID, DESTINATION_DEVICE_ID,
-          duplicateMessage);
-      final long secondId = messagesCache.insert(duplicateGuid, DESTINATION_UUID, DESTINATION_DEVICE_ID,
-          duplicateMessage);
+      messagesCache.insert(duplicateGuid, DESTINATION_UUID, DESTINATION_DEVICE_ID, duplicateMessage);
+      messagesCache.insert(duplicateGuid, DESTINATION_UUID, DESTINATION_DEVICE_ID, duplicateMessage);
 
-      assertEquals(firstId, secondId);
+      assertEquals(1, messagesCache.getAllMessages(DESTINATION_UUID, DESTINATION_DEVICE_ID, 0)
+          .count()
+          .blockOptional()
+          .orElse(0L));
     }
 
     @ParameterizedTest