diff --git a/lib/reducers/message-reducer.js b/lib/reducers/message-reducer.js
--- a/lib/reducers/message-reducer.js
+++ b/lib/reducers/message-reducer.js
@@ -92,11 +92,8 @@
   processUpdatesActionType,
 } from '../types/update-types';
 import { setNewSessionActionType } from '../utils/action-utils';
-import { isDev } from '../utils/dev-utils';
 import { translateClientDBMessageInfosToRawMessageInfos } from '../utils/message-ops-utils';
-import { assertObjectsAreEqual } from '../utils/objects';
 
-const PROCESSED_MSG_STORE_INVARIANTS_DISABLED = !isDev;
 const _mapValuesWithKeys = _mapValues.convert({ cap: false });
 
 // Input must already be ordered!
@@ -128,22 +125,6 @@
   );
 }
 
-function assertMessageStoreMessagesAreEqual(
-  processedMessageStore: MessageStore,
-  expectedMessageStore: MessageStore,
-  location: string,
-) {
-  if (PROCESSED_MSG_STORE_INVARIANTS_DISABLED) {
-    return;
-  }
-
-  assertObjectsAreEqual(
-    processedMessageStore.messages,
-    expectedMessageStore.messages,
-    `MessageStore.messages - ${location}`,
-  );
-}
-
 type FreshMessageStoreResult = {
   +messageStoreOperations: $ReadOnlyArray<MessageStoreOperation>,
   +messageStore: MessageStore,
@@ -282,11 +263,10 @@
   newMessageInfos: $ReadOnlyArray<RawMessageInfo>,
   truncationStatus: { [threadID: string]: MessageTruncationStatus },
   threadInfos: { +[threadID: string]: RawThreadInfo },
-  actionType: *,
 ): MergeNewMessagesResult {
   const {
     messageStoreOperations: updateWithLatestThreadInfosOps,
-    messageStore: updatedMessageStore,
+    messageStore: messageStoreUpdatedWithLatestThreadInfos,
     reassignedThreadIDs,
   } = updateMessageStoreWithLatestThreadInfos(oldMessageStore, threadInfos);
 
@@ -294,11 +274,11 @@
     oldMessageStore,
     updateWithLatestThreadInfosOps,
   );
-  assertMessageStoreMessagesAreEqual(
-    messageStoreAfterUpdateOps,
-    updatedMessageStore,
-    `${actionType}| reassignment and filtering`,
-  );
+
+  const updatedMessageStore = {
+    ...messageStoreUpdatedWithLatestThreadInfos,
+    messages: messageStoreAfterUpdateOps.messages,
+  };
 
   const localIDsToServerIDs: Map<string, string> = new Map();
 
@@ -754,7 +734,6 @@
       messagesResult.rawMessageInfos,
       messagesResult.truncationStatuses,
       newThreadInfos,
-      action.type,
     );
     return { messageStoreOperations, messageStore: mergedMessageStore };
   } else if (action.type === processUpdatesActionType) {
@@ -775,7 +754,6 @@
       messagesResult.rawMessageInfos,
       messagesResult.truncationStatuses,
       newThreadInfos,
-      action.type,
     );
     return {
       messageStoreOperations,
@@ -799,7 +777,6 @@
       messagesResult.rawMessageInfos,
       messagesResult.truncationStatuses,
       newThreadInfos,
-      action.type,
     );
     return { messageStoreOperations, messageStore: mergedMessageStore };
   } else if (
@@ -813,7 +790,6 @@
       action.payload.rawMessageInfos,
       action.payload.truncationStatuses,
       newThreadInfos,
-      action.type,
     );
     return { messageStoreOperations, messageStore: mergedMessageStore };
   } else if (
@@ -828,7 +804,6 @@
       action.payload.rawMessageInfos,
       { [action.payload.threadID]: action.payload.truncationStatus },
       newThreadInfos,
-      action.type,
     );
     return { messageStoreOperations, messageStore: mergedMessageStore };
   } else if (
@@ -868,7 +843,6 @@
       messagesResult.rawMessageInfos,
       messagesResult.truncationStatuses,
       newThreadInfos,
-      action.type,
     );
     return { messageStoreOperations, messageStore: mergedMessageStore };
   } else if (action.type === registerActionTypes.success) {
@@ -885,7 +859,6 @@
       action.payload.rawMessageInfos,
       truncationStatuses,
       newThreadInfos,
-      action.type,
     );
     return { messageStoreOperations, messageStore: mergedMessageStore };
   } else if (
@@ -901,7 +874,6 @@
       action.payload.newMessageInfos,
       { [action.payload.threadID]: messageTruncationStatus.UNCHANGED },
       newThreadInfos,
-      action.type,
     );
     return { messageStoreOperations, messageStore: mergedMessageStore };
   } else if (
@@ -916,7 +888,6 @@
       action.payload.newMessageInfos,
       { [action.payload.threadID]: messageTruncationStatus.UNCHANGED },
       newThreadInfos,
-      action.type,
     );
     return { messageStoreOperations, messageStore: mergedMessageStore };
   } else if (action.type === deleteEntryActionTypes.success) {
@@ -930,7 +901,6 @@
         payload.newMessageInfos,
         { [payload.threadID]: messageTruncationStatus.UNCHANGED },
         newThreadInfos,
-        action.type,
       );
       return { messageStoreOperations, messageStore: mergedMessageStore };
     }
@@ -944,7 +914,6 @@
       action.payload.newMessageInfos,
       { [threadID]: messageTruncationStatus.UNCHANGED },
       newThreadInfos,
-      action.type,
     );
     return { messageStoreOperations, messageStore: mergedMessageStore };
   } else if (action.type === joinThreadActionTypes.success) {
@@ -960,7 +929,6 @@
       messagesResult.rawMessageInfos,
       messagesResult.truncationStatuses,
       newThreadInfos,
-      action.type,
     );
     return { messageStoreOperations, messageStore: mergedMessageStore };
   } else if (
@@ -1158,7 +1126,6 @@
       action.payload.rawMessageInfos,
       truncationStatuses,
       newThreadInfos,
-      action.type,
     );
     return {
       messageStoreOperations,