diff --git a/js/modules/messages_data_migrator.js b/js/modules/messages_data_migrator.js
index e3ce66c89d..1ba211e0fd 100644
--- a/js/modules/messages_data_migrator.js
+++ b/js/modules/messages_data_migrator.js
@@ -1,12 +1,20 @@
+/* eslint-env browser */
+
 const isFunction = require('lodash/isFunction');
 const isNumber = require('lodash/isNumber');
 const isObject = require('lodash/isObject');
 const isString = require('lodash/isString');
+const last = require('lodash/last');
 
 const Message = require('./types/message');
 const { deferredToPromise } = require('./deferred_to_promise');
-const Migrations0DatabaseWithAttachmentData =
-  require('./migrations/migrations_0_database_with_attachment_data');
+
+
+const DATABASE_NAME = 'signal';
+// Last version with attachment data stored in database:
+const EXPECTED_DATABASE_VERSION = 17;
+const MESSAGES_STORE_NAME = 'messages';
+const ITEMS_STORE_NAME = 'items';
 
 exports.processNext = async ({
   BackboneMessage,
@@ -44,7 +52,7 @@ exports.processNext = async ({
   const upgradeDuration = Date.now() - startUpgradeTime;
 
   const startSaveTime = Date.now();
-  const saveMessage = _saveMessage({ BackboneMessage });
+  const saveMessage = _saveMessageBackbone({ BackboneMessage });
   await Promise.all(upgradedMessages.map(saveMessage));
   const saveDuration = Date.now() - startSaveTime;
 
@@ -78,20 +86,91 @@ exports.processAll = async ({
     throw new TypeError('"upgradeMessageSchema" is required');
   }
 
-  const lastIndex = null;
-  const unprocessedMessages =
-    await _dangerouslyFetchMessagesRequiringSchemaUpgradeWithoutIndex({
-      Backbone,
-      count: 10,
-      lastIndex,
+  const connection = await openDatabase(DATABASE_NAME, EXPECTED_DATABASE_VERSION);
+  const isComplete = await isMigrationComplete(connection);
+  console.log('Is attachment migration complete?', isComplete);
+  if (isComplete) {
+    return;
+  }
+
+  const migrationStartTime = Date.now();
+  let unprocessedMessages = [];
+  do {
+    // eslint-disable-next-line no-await-in-loop
+    const lastProcessedIndex = (await getLastProcessedIndex(connection)) || null;
+
+    const fetchUnprocessedMessagesStartTime = Date.now();
+    unprocessedMessages =
+      // eslint-disable-next-line no-await-in-loop
+      await _dangerouslyFetchMessagesRequiringSchemaUpgradeWithoutIndex({
+        connection,
+        count: 10,
+        lastIndex: lastProcessedIndex,
+      });
+    const fetchDuration = Date.now() - fetchUnprocessedMessagesStartTime;
+    const numUnprocessedMessages = unprocessedMessages.length;
+
+    const upgradeStartTime = Date.now();
+    const upgradedMessages =
+      // eslint-disable-next-line no-await-in-loop
+      await Promise.all(unprocessedMessages.map(upgradeMessageSchema));
+    const upgradeDuration = Date.now() - upgradeStartTime;
+
+    const saveMessagesStartTime = Date.now();
+    const transaction = connection.transaction(MESSAGES_STORE_NAME, 'readwrite');
+    const transactionCompletion = completeTransaction(transaction);
+    // eslint-disable-next-line no-await-in-loop
+    await Promise.all(upgradedMessages.map(_saveMessage({ transaction })));
+    // eslint-disable-next-line no-await-in-loop
+    await transactionCompletion;
+    const saveDuration = Date.now() - saveMessagesStartTime;
+
+    // TODO: Confirm transaction is complete
+
+    const lastMessage = last(upgradedMessages);
+    const newLastProcessedIndex = lastMessage ? lastMessage.id : null;
+    if (newLastProcessedIndex) {
+      // eslint-disable-next-line no-await-in-loop
+      await setLastProcessedIndex(connection, newLastProcessedIndex);
+    }
+
+    console.log('Upgrade message schema on startup:', {
+      lastProcessedIndex,
+      numUnprocessedMessages,
+      fetchDuration,
+      saveDuration,
+      upgradeDuration,
+      newLastProcessedIndex,
     });
+  } while (unprocessedMessages.length > 0);
+
+  await markMigrationComplete(connection);
+  connection.close();
+
+  const totalDuration = Date.now() - migrationStartTime;
+  console.log('Attachment migration complete:', { totalDuration });
 };
 
-const _saveMessage = ({ BackboneMessage } = {}) => (message) => {
+const _saveMessageBackbone = ({ BackboneMessage } = {}) => (message) => {
   const backboneMessage = new BackboneMessage(message);
   return deferredToPromise(backboneMessage.save());
 };
 
+const _saveMessage = ({ transaction } = {}) => (message) => {
+  if (!isObject(transaction)) {
+    throw new TypeError('"transaction" is required');
+  }
+
+  const messagesStore = transaction.objectStore(MESSAGES_STORE_NAME);
+  const request = messagesStore.put(message, message.id);
+  return new Promise((resolve, reject) => {
+    request.onsuccess = () =>
+      resolve();
+    request.onerror = event =>
+      reject(event.target.error);
+  });
+};
+
 const _fetchMessagesRequiringSchemaUpgrade =
   async ({ BackboneMessageCollection, count } = {}) => {
     if (!isFunction(BackboneMessageCollection)) {
@@ -119,11 +198,10 @@ const _fetchMessagesRequiringSchemaUpgrade =
     }));
   };
 
-const MAX_MESSAGE_KEY = 'ffffffff-ffff-ffff-ffff-ffffffffffff';
 const _dangerouslyFetchMessagesRequiringSchemaUpgradeWithoutIndex =
-  async ({ Backbone, count, lastIndex } = {}) => {
-    if (!isObject(Backbone)) {
-      throw new TypeError('"Backbone" is required');
+  ({ connection, count, lastIndex } = {}) => {
+    if (!isObject(connection)) {
+      throw new TypeError('"connection" is required');
     }
 
     if (!isNumber(count)) {
@@ -134,17 +212,112 @@ const _dangerouslyFetchMessagesRequiringSchemaUpgradeWithoutIndex =
       throw new TypeError('"lastIndex" must be a string');
     }
 
-    const storeName = 'messages';
-    const collection =
-      Migrations0DatabaseWithAttachmentData.createCollection({ Backbone, storeName });
+    const hasLastIndex = Boolean(lastIndex);
 
-    const range = lastIndex ? [lastIndex, MAX_MESSAGE_KEY] : null;
-    await deferredToPromise(collection.fetch({
-      limit: count,
-      range,
-    }));
+    const transaction = connection.transaction(MESSAGES_STORE_NAME, 'readonly');
+    const messagesStore = transaction.objectStore(MESSAGES_STORE_NAME);
 
-    const models = collection.models || [];
-    const messages = models.map(model => model.toJSON());
-    return messages;
+    const excludeLowerBound = true;
+    const query = hasLastIndex
+      ? IDBKeyRange.lowerBound(lastIndex, excludeLowerBound)
+      : undefined;
+    const request = messagesStore.getAll(query, count);
+    return new Promise((resolve, reject) => {
+      request.onsuccess = event =>
+        resolve(event.target.result);
+      request.onerror = event =>
+        reject(event.target.error);
+    });
   };
+
+const openDatabase = (name, version) => {
+  const request = window.indexedDB.open(name, version);
+  return new Promise((resolve, reject) => {
+    request.onblocked = () =>
+      reject(new Error('Database blocked'));
+
+    request.onupgradeneeded = event =>
+      reject(new Error('Unexpected database upgrade required:' +
+        `oldVersion: ${event.oldVersion}, newVersion: ${event.newVersion}`));
+
+    request.onerror = event =>
+      reject(event.target.error);
+
+    request.onsuccess = (event) => {
+      const connection = event.target.result;
+      resolve(connection);
+    };
+  });
+};
+
+const LAST_PROCESSED_INDEX_KEY = 'attachmentMigration_lastProcessedIndex';
+const IS_MIGRATION_COMPLETE_KEY = 'attachmentMigration_isComplete';
+
+const getLastProcessedIndex = connection =>
+  getItem(connection, LAST_PROCESSED_INDEX_KEY);
+
+const setLastProcessedIndex = (connection, value) =>
+  setItem(connection, LAST_PROCESSED_INDEX_KEY, value);
+
+const isMigrationComplete = async (connection) => {
+  const value = await getItem(connection, IS_MIGRATION_COMPLETE_KEY);
+  return Boolean(value);
+};
+
+const markMigrationComplete = connection =>
+  setItem(connection, IS_MIGRATION_COMPLETE_KEY, true);
+
+const getItem = (connection, key) => {
+  if (!isObject(connection)) {
+    throw new TypeError('"connection" is required');
+  }
+
+  if (!isString(key)) {
+    throw new TypeError('"key" must be a string');
+  }
+
+  const transaction = connection.transaction(ITEMS_STORE_NAME, 'readonly');
+  const itemsStore = transaction.objectStore(ITEMS_STORE_NAME);
+  const request = itemsStore.get(key);
+  return new Promise((resolve, reject) => {
+    request.onerror = event =>
+      reject(event.target.error);
+
+    request.onsuccess = event =>
+      resolve(event.target.result);
+  });
+};
+
+const setItem = (connection, key, value) => {
+  if (!isObject(connection)) {
+    throw new TypeError('"connection" is required');
+  }
+
+  if (!isString(key)) {
+    throw new TypeError('"key" must be a string');
+  }
+
+  const transaction = connection.transaction(ITEMS_STORE_NAME, 'readwrite');
+  const itemsStore = transaction.objectStore(ITEMS_STORE_NAME);
+  const request = itemsStore.put(value, key);
+  return new Promise((resolve, reject) => {
+    request.onerror = event =>
+      reject(event.target.error);
+
+    request.onsuccess = () =>
+      resolve();
+  });
+};
+
+const completeTransaction = transaction =>
+  new Promise((resolve, reject) => {
+    // eslint-disable-next-line no-param-reassign
+    transaction.onabort = event =>
+      reject(event.target.error);
+    // eslint-disable-next-line no-param-reassign
+    transaction.onerror = event =>
+      reject(event.target.error);
+    // eslint-disable-next-line no-param-reassign
+    transaction.oncomplete = () =>
+      resolve();
+  });