diff --git a/lib/hooks/message-author.js b/lib/hooks/message-author.js
new file mode 100644
--- /dev/null
+++ b/lib/hooks/message-author.js
@@ -0,0 +1,59 @@
+// @flow
+
+import * as React from 'react';
+
+import { useBaseGetLatestMessageEdit } from './latest-message-edit.js';
+import type { MessageStore } from '../types/message-types.js';
+import { messageIDIsThick } from '../types/message-types.js';
+import { useSelector } from '../utils/redux-utils.js';
+
+const messageAuthorCache = new Map<string, string>();
+
+function useGetMessageAuthor(): (
+  messageID: string,
+) => ?string | Promise<?string> {
+  const messageStore = useSelector(state => state.messageStore);
+  const baseGetMessageAuthor = useBaseGetMessageAuthor();
+  return React.useCallback(
+    (messageID: string) => baseGetMessageAuthor(messageID, messageStore),
+    [baseGetMessageAuthor, messageStore],
+  );
+}
+
+function useBaseGetMessageAuthor(): (
+  messageID: string,
+  messageStore: MessageStore,
+) => ?string | Promise<?string> {
+  const baseGetLatestMessageEdit = useBaseGetLatestMessageEdit();
+  return React.useCallback(
+    (messageID: string, messageStore: MessageStore) => {
+      const messageFromRedux = messageStore.messages[messageID];
+      if (messageFromRedux) {
+        return messageFromRedux.creatorID;
+      }
+      if (!messageIDIsThick(messageID)) {
+        // For thin threads, everything in SQLite should also be in Redux, so
+        // there is no point trying to query SQLite if it's not in Redux
+        return null;
+      }
+      const messageAuthorFromCache = messageAuthorCache.get(messageID);
+      if (messageAuthorFromCache) {
+        return messageAuthorFromCache;
+      }
+      return (async () => {
+        const rawMessageInfo = await baseGetLatestMessageEdit(
+          messageID,
+          messageStore,
+        );
+        const creatorID = rawMessageInfo?.creatorID;
+        if (creatorID) {
+          messageAuthorCache.set(messageID, creatorID);
+        }
+        return creatorID;
+      })();
+    },
+    [baseGetLatestMessageEdit],
+  );
+}
+
+export { useGetMessageAuthor, useBaseGetMessageAuthor };
diff --git a/lib/hooks/message-hooks.js b/lib/hooks/message-hooks.js
--- a/lib/hooks/message-hooks.js
+++ b/lib/hooks/message-hooks.js
@@ -2,7 +2,7 @@
 
 import * as React from 'react';
 
-import { useGetLatestMessageEdit } from './latest-message-edit.js';
+import { useGetMessageAuthor } from './message-author.js';
 import { messageInfoSelector } from '../selectors/chat-selectors.js';
 import {
   getOldestNonLocalMessageID,
@@ -40,7 +40,7 @@
   const messageInfos = useSelector(messageInfoSelector);
   const messageStore = useSelector(state => state.messageStore);
   const viewerID = useSelector(state => state.currentUserInfo?.id);
-  const fetchMessage = useGetLatestMessageEdit();
+  const getMessageAuthor = useGetMessageAuthor();
   return React.useCallback(
     async threadInfo => {
       if (!viewerID) {
@@ -53,7 +53,7 @@
       const showInMessagePreviewParams = {
         threadInfo,
         viewerID,
-        fetchMessage,
+        getMessageAuthor,
       };
       let mostRecentMessageInfo;
       for (const messageID of thread.messageIDs) {
@@ -92,7 +92,7 @@
         shouldFetchOlderMessages: true,
       };
     },
-    [messageInfos, messageStore, viewerID, fetchMessage],
+    [messageInfos, messageStore, viewerID, getMessageAuthor],
   );
 }
 
diff --git a/lib/hooks/thread-time.js b/lib/hooks/thread-time.js
--- a/lib/hooks/thread-time.js
+++ b/lib/hooks/thread-time.js
@@ -2,7 +2,7 @@
 
 import * as React from 'react';
 
-import { useBaseGetLatestMessageEdit } from './latest-message-edit.js';
+import { useBaseGetMessageAuthor } from './message-author.js';
 import { messageSpecs } from '../shared/messages/message-specs.js';
 import type {
   MessageInfo,
@@ -19,7 +19,7 @@
   messages: { +[id: string]: ?MessageInfo | RawMessageInfo },
 ) => LastUpdatedTimes {
   const viewerID = useSelector(state => state.currentUserInfo?.id);
-  const baseGetLatestMessageEdit = useBaseGetLatestMessageEdit();
+  const baseGetMessageAuthor = useBaseGetMessageAuthor();
   return React.useCallback(
     (threadInfo, messageStore, messages) => {
       // This callback returns three variables:
@@ -47,8 +47,8 @@
       const getLastUpdatedTimeParams = {
         threadInfo,
         viewerID,
-        fetchMessage: (messageID: string) =>
-          baseGetLatestMessageEdit(messageID, messageStore),
+        getMessageAuthor: (messageID: string) =>
+          baseGetMessageAuthor(messageID, messageStore),
       };
 
       let lastUpdatedTime: ?() => Promise<?number>;
@@ -128,7 +128,7 @@
         lastUpdatedTime: lastUpdatedWithFallback,
       };
     },
-    [viewerID, baseGetLatestMessageEdit],
+    [viewerID, baseGetMessageAuthor],
   );
 }
 
diff --git a/lib/shared/messages/message-spec.js b/lib/shared/messages/message-spec.js
--- a/lib/shared/messages/message-spec.js
+++ b/lib/shared/messages/message-spec.js
@@ -85,7 +85,7 @@
 export type ShowInMessagePreviewParams = {
   +threadInfo: ThreadInfo,
   +viewerID: string,
-  +fetchMessage: (messageID: string) => Promise<?RawMessageInfo>,
+  +getMessageAuthor: (messageID: string) => ?string | Promise<?string>,
 };
 
 export type MessageSpec<Data, RawInfo, Info> = {
diff --git a/lib/shared/messages/reaction-message-spec.js b/lib/shared/messages/reaction-message-spec.js
--- a/lib/shared/messages/reaction-message-spec.js
+++ b/lib/shared/messages/reaction-message-spec.js
@@ -232,17 +232,23 @@
 
   validator: rawReactionMessageInfoValidator,
 
-  showInMessagePreview: async (
+  showInMessagePreview: (
     messageInfo: ReactionMessageInfo,
     params: ShowInMessagePreviewParams,
   ) => {
-    const originalMessage = await params.fetchMessage(
+    const getOriginalMessageAuthorResult = params.getMessageAuthor(
       messageInfo.targetMessageID,
     );
-    if (!originalMessage) {
+    if (!getOriginalMessageAuthorResult) {
       return false;
     }
-    return originalMessage.creatorID === params.viewerID;
+    if (typeof getOriginalMessageAuthorResult === 'string') {
+      return getOriginalMessageAuthorResult === params.viewerID;
+    }
+    return (async () => {
+      const originalMessageAuthor = await getOriginalMessageAuthorResult;
+      return originalMessageAuthor === params.viewerID;
+    })();
   },
 
   getLastUpdatedTime:
@@ -251,13 +257,19 @@
       params: ShowInMessagePreviewParams,
     ) =>
     async () => {
-      const originalMessage = await params.fetchMessage(
+      const getOriginalMessageAuthorResult = params.getMessageAuthor(
         messageInfo.targetMessageID,
       );
-      if (!originalMessage) {
+      if (!getOriginalMessageAuthorResult) {
         return null;
       }
-      return originalMessage.creatorID === params.viewerID
+      if (typeof getOriginalMessageAuthorResult === 'string') {
+        return getOriginalMessageAuthorResult === params.viewerID
+          ? messageInfo.time
+          : null;
+      }
+      const originalMessageAuthor = await getOriginalMessageAuthorResult;
+      return originalMessageAuthor === params.viewerID
         ? messageInfo.time
         : null;
     },
diff --git a/lib/types/message-types.js b/lib/types/message-types.js
--- a/lib/types/message-types.js
+++ b/lib/types/message-types.js
@@ -144,7 +144,13 @@
 import { rawUpdateRelationshipMessageInfoValidator } from './messages/update-relationship.js';
 import { type RelativeUserInfo, type UserInfos } from './user-types.js';
 import { values } from '../utils/objects.js';
-import { tID, tNumber, tShape, tUserID } from '../utils/validation-utils.js';
+import {
+  tID,
+  tNumber,
+  tShape,
+  tUserID,
+  thickIDRegex,
+} from '../utils/validation-utils.js';
 
 const composableMessageTypes = new Set([
   messageTypes.TEXT,
@@ -709,3 +715,7 @@
   +messages: $ReadOnlyArray<RawMessageInfo>,
   +endReached: boolean,
 };
+
+export function messageIDIsThick(messageID: string): boolean {
+  return thickIDRegex.test(messageID);
+}