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
@@ -92,7 +92,6 @@
   fullStateSyncActionType,
   incrementalStateSyncActionType,
 } from '../types/socket-types.js';
-import { updateThreadLastNavigatedActionType } from '../types/thread-activity-types.js';
 import { threadPermissions } from '../types/thread-permission-types.js';
 import { type RawThreadInfo } from '../types/thread-types.js';
 import {
@@ -156,8 +155,6 @@
 const newThread = () => ({
   messageIDs: [],
   startReached: false,
-  lastNavigatedTo: 0,
-  lastPruned: Date.now(),
 });
 
 type FreshMessageStoreResult = {
@@ -518,8 +515,6 @@
         updatedThreads[threadID] = {
           messageIDs,
           startReached: false,
-          lastNavigatedTo: oldThread.lastNavigatedTo,
-          lastPruned: oldThread.lastPruned,
         };
         return updatedThreads[threadID];
       }
@@ -543,8 +538,6 @@
         updatedThreads[threadID] = {
           messageIDs: oldMessageIDs,
           startReached,
-          lastNavigatedTo: oldThread.lastNavigatedTo,
-          lastPruned: oldThread.lastPruned,
         };
         return updatedThreads[threadID];
       }
@@ -553,8 +546,6 @@
       return {
         messageIDs: mergedMessageIDs,
         startReached,
-        lastNavigatedTo: oldThread.lastNavigatedTo,
-        lastPruned: oldThread.lastPruned,
       };
     }),
     _pickBy(thread => !!thread),
@@ -1008,7 +999,6 @@
       },
     ];
 
-    const now = Date.now();
     let updatedThreads;
     let local = { ...messageStore.local };
     if (messageStore.messages[localID]) {
@@ -1021,8 +1011,6 @@
         [threadID]: {
           messageIDs: sortMessageIDs(messages)(messageIDs),
           startReached: thread?.startReached ?? true,
-          lastNavigatedTo: thread?.lastNavigatedTo ?? now,
-          lastPruned: thread?.lastPruned ?? now,
         },
       };
     } else {
@@ -1035,8 +1023,6 @@
           : {
               messageIDs: [localID],
               startReached: true,
-              lastNavigatedTo: now,
-              lastPruned: now,
             },
       };
     }
@@ -1541,7 +1527,6 @@
 
     const messageIDs =
       messageStore.threads[messageInfo.threadID]?.messageIDs ?? [];
-    const now = Date.now();
     const threadState: ThreadMessageInfo = messageStore.threads[threadID]
       ? {
           ...messageStore.threads[threadID],
@@ -1550,8 +1535,6 @@
       : {
           messageIDs: [localID],
           startReached: true,
-          lastNavigatedTo: now,
-          lastPruned: now,
         };
 
     const messageStoreOperations = [
@@ -1738,32 +1721,6 @@
       messageStoreOperations,
       messageStore: processedMessageStore,
     };
-  } else if (action.type === updateThreadLastNavigatedActionType) {
-    const { threadID, time } = action.payload;
-    if (!messageStore.threads[threadID]) {
-      return { messageStoreOperations: [], messageStore };
-    }
-
-    const updatedThreads = {
-      [threadID]: {
-        ...messageStore.threads[threadID],
-        lastNavigatedTo: time,
-      },
-    };
-
-    const messageStoreOperations = [
-      {
-        type: 'replace_threads',
-        payload: { threads: updatedThreads },
-      },
-    ];
-
-    const processedMessageStore = processMessageStoreOperations(
-      messageStore,
-      messageStoreOperations,
-    );
-
-    return { messageStoreOperations, messageStore: processedMessageStore };
   }
   return { messageStoreOperations: [], messageStore };
 }
diff --git a/lib/reducers/message-reducer.test.js b/lib/reducers/message-reducer.test.js
--- a/lib/reducers/message-reducer.test.js
+++ b/lib/reducers/message-reducer.test.js
@@ -42,8 +42,6 @@
     '91140': {
       messageIDs: ['local1'],
       startReached: true,
-      lastNavigatedTo: 1639522314170,
-      lastPruned: 1639522292271,
     },
   },
   local: {},
@@ -271,8 +269,6 @@
     '88471': {
       messageIDs: ['local11', 'local10', '103502'],
       startReached: false,
-      lastNavigatedTo: 1658172614602,
-      lastPruned: 1658169913623,
     },
   };
 
diff --git a/lib/shared/message-utils.js b/lib/shared/message-utils.js
--- a/lib/shared/message-utils.js
+++ b/lib/shared/message-utils.js
@@ -482,8 +482,6 @@
   return {
     messageIDs: mergedMessageIDs,
     startReached: first.startReached && second.startReached,
-    lastNavigatedTo: Math.max(first.lastNavigatedTo, second.lastNavigatedTo),
-    lastPruned: Math.max(first.lastPruned, second.lastPruned),
   };
 }
 
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
@@ -388,15 +388,11 @@
 export type ThreadMessageInfo = {
   messageIDs: string[],
   startReached: boolean,
-  lastNavigatedTo: number, // millisecond timestamp
-  lastPruned: number, // millisecond timestamp
 };
 const threadMessageInfoValidator: TInterface<ThreadMessageInfo> =
   tShape<ThreadMessageInfo>({
     messageIDs: t.list(tID),
     startReached: t.Boolean,
-    lastNavigatedTo: t.Number,
-    lastPruned: t.Number,
   });
 
 // Tracks client-local information about a message that hasn't been assigned an
diff --git a/lib/utils/message-ops-utils.js b/lib/utils/message-ops-utils.js
--- a/lib/utils/message-ops-utils.js
+++ b/lib/utils/message-ops-utils.js
@@ -243,8 +243,6 @@
 
 type TranslatedThreadMessageInfo = {
   +startReached: boolean,
-  +lastNavigatedTo: number,
-  +lastPruned: number,
 };
 export type TranslatedThreadMessageInfos = {
   +[threadID: string]: TranslatedThreadMessageInfo,
@@ -257,8 +255,6 @@
       threadInfo.id,
       {
         startReached: threadInfo.start_reached === '1',
-        lastNavigatedTo: parseInt(threadInfo.last_navigated_to),
-        lastPruned: parseInt(threadInfo.last_pruned),
       },
     ]),
   );
@@ -269,8 +265,8 @@
   threadMessageInfo: ThreadMessageInfo | TranslatedThreadMessageInfo,
 ): ClientDBThreadMessageInfo {
   const startReached = threadMessageInfo.startReached ? 1 : 0;
-  const lastNavigatedTo = threadMessageInfo.lastNavigatedTo ?? 0;
-  const lastPruned = threadMessageInfo.lastPruned ?? 0;
+  const lastNavigatedTo = 0;
+  const lastPruned = 0;
   return {
     id,
     start_reached: startReached.toString(),
diff --git a/native/redux/persist.js b/native/redux/persist.js
--- a/native/redux/persist.js
+++ b/native/redux/persist.js
@@ -799,8 +799,6 @@
 // eslint-disable-next-line no-unused-vars
 type PersistedThreadMessageInfo = {
   +startReached: boolean,
-  +lastNavigatedTo: number,
-  +lastPruned: number,
 };
 type PersistedMessageStore = {
   +local: { +[id: string]: LocalMessageInfo },
diff --git a/web/redux/redux-setup.js b/web/redux/redux-setup.js
--- a/web/redux/redux-setup.js
+++ b/web/redux/redux-setup.js
@@ -333,16 +333,6 @@
     const now = Date.now();
     state = {
       ...state,
-      messageStore: {
-        ...state.messageStore,
-        threads: {
-          ...state.messageStore.threads,
-          [activeThread]: {
-            ...state.messageStore.threads[activeThread],
-            lastNavigatedTo: now,
-          },
-        },
-      },
       threadActivityStore: {
         ...state.threadActivityStore,
         [activeThread]: {