diff --git a/js/modules/messages_migration.js b/js/modules/messages_migration.js
new file mode 100644
index 000000000..c1b4f3e0d
--- /dev/null
+++ b/js/modules/messages_migration.js
@@ -0,0 +1,99 @@
+const isNumber = require('lodash/isNumber');
+const isFunction = require('lodash/isFunction');
+const Message = require('./types/message');
+
+
+const processNext = async ({
+  BackboneMessage,
+  BackboneMessageCollection,
+  count,
+  upgradeMessageSchema,
+  wrapDeferred,
+} = {}) => {
+  if (!isFunction(BackboneMessage)) {
+    throw new TypeError('`BackboneMessage` (Whisper.Message) constructor is required');
+  }
+
+  if (!isFunction(BackboneMessageCollection)) {
+    throw new TypeError('`BackboneMessageCollection` (Whisper.MessageCollection)' +
+      ' constructor is required');
+  }
+
+  if (!isNumber(count)) {
+    throw new TypeError('`count` is required');
+  }
+
+  if (!isFunction(upgradeMessageSchema)) {
+    throw new TypeError('`upgradeMessageSchema` is required');
+  }
+
+  if (!isFunction(wrapDeferred)) {
+    throw new TypeError('`wrapDeferred` is required');
+  }
+
+  const startTime = Date.now();
+
+  const startFetchTime = Date.now();
+  const messagesRequiringSchemaUpgrade =
+    await _fetchMessagesRequiringSchemaUpgrade({ BackboneMessageCollection, count });
+  const fetchDuration = Date.now() - startFetchTime;
+
+  const startUpgradeTime = Date.now();
+  const upgradedMessages =
+    await Promise.all(messagesRequiringSchemaUpgrade.map(upgradeMessageSchema));
+  const upgradeDuration = Date.now() - startUpgradeTime;
+
+  const startSaveTime = Date.now();
+  const saveMessage = _saveMessage({ BackboneMessage, wrapDeferred });
+  await Promise.all(upgradedMessages.map(saveMessage));
+  const saveDuration = Date.now() - startSaveTime;
+
+  const totalDuration = Date.now() - startTime;
+  const numProcessed = messagesRequiringSchemaUpgrade.length;
+  const hasMore = numProcessed > 0;
+  return {
+    hasMore,
+    numProcessed,
+    fetchDuration,
+    upgradeDuration,
+    saveDuration,
+    totalDuration,
+  };
+};
+
+const _saveMessage = ({ BackboneMessage, wrapDeferred } = {}) => (message) => {
+  const backboneMessage = new BackboneMessage(message);
+  return wrapDeferred(backboneMessage.save());
+};
+
+const _fetchMessagesRequiringSchemaUpgrade =
+  async ({ BackboneMessageCollection, count } = {}) => {
+    if (!isFunction(BackboneMessageCollection)) {
+      throw new TypeError('`BackboneMessageCollection` (Whisper.MessageCollection)' +
+        ' constructor is required');
+    }
+
+    if (!isNumber(count)) {
+      throw new TypeError('`count` is required');
+    }
+
+    const collection = new BackboneMessageCollection();
+    return new Promise(resolve => collection.fetch({
+      limit: count,
+      index: {
+        name: 'schemaVersion',
+        upper: Message.CURRENT_SCHEMA_VERSION,
+        excludeUpper: true,
+        order: 'desc',
+      },
+    }).always(() => {
+      const models = collection.models || [];
+      const messages = models.map(model => model.toJSON());
+      resolve(messages);
+    }));
+  };
+
+
+module.exports = {
+  processNext,
+};