PowerSync Migration 2026 — check your code for free

PowerSync migration: 6 findings in one 22-line orders.ts, which is what a React Native, web, Swift, Kotlin or Flutter developer still on MongoDB Realm Sync gets from the free check before writing a line of PowerSync code.

What MongoDB changed, and when

In September 2024 MongoDB deprecated Atlas Device Sync, the sync side of the Atlas Device SDKs (Realm), the Atlas Data API and custom HTTPS Endpoints. All of them reached end-of-life on 2025-09-30. Since that day a client that logs in through Realm.App, opens a Flexible Sync session or posts to data.mongodb-api.com gets no sync. PowerSync's MongoDB module reached general availability in March 2025 and is the path MongoDB pointed Device Sync users to.

The local database is a different story. The Realm SDKs stayed open source, and a local-only Realm still opens and queries. That is why the first job of a migration is a list: which lines are dead, and which ones are fine.

The sample file

The sample is a small offline order list written for Device Sync:

import * as Realm from 'realm-web';
const app = new Realm.App({ id: 'orders-abcde' });
const user = await app.logIn(Realm.Credentials.anonymous());
const mongo = user.mongoClient('mongodb-atlas');
const DATA_API = 'https://data.mongodb-api.com/app/orders-abcde/endpoint/data/v1';
const res = await fetch(`${DATA_API}/action/find`, { ... });

The check returns 6 findings, one per line above:

1. RS01 realm-web import: replace with @powersync/web (or @powersync/react-native).
2. RS02 new Realm.App: replace with new PowerSyncDatabase({ schema, database: { dbFilename } }) and db.connect(connector).
3. RS10 Realm.Credentials.anonymous(): keep your own auth provider and return its JWT from fetchCredentials().
4. RS11 user.mongoClient('mongodb-atlas'): query the local SQLite copy with db.getAll('SELECT ...').
5. RS06 the Data API base URL: call your own backend with the MongoDB driver.
6. RS09 /action/find: reads become db.getAll or db.watch, writes become db.execute, uploaded by connector.uploadData().

Each message ends with the clock. With the date set to 2026-09-29 it reads "Stopped 2025-09-30 (364 days before 2026-09-29)". With a date before the end-of-life the same finding is a warning with the days left.

Why not grep for realm

A grep for realm flags every schema class and every local query you can keep. The 16 rules fire only on the paths that stopped: realm-web and the native sync SDKs used with sync, Realm.App, Realm.Credentials, mongoClient, Flexible Sync configuration, subscriptions, partitionValue, syncSession, user.functions, @realm/react AppProvider and UserProvider, the Data API base URL, Data API actions, the api-key header, custom HTTPS Endpoints and the App Services client API URL. Comment lines are skipped, and a clean PowerSync version of the same file returns 0 findings.

What the PowerSync side looks like

The replacement for the sample is one PowerSyncDatabase with a Schema of Tables, a connector with fetchCredentials() returning your endpoint and JWT, and uploadData() sending each CRUD transaction to your own API. Which rows each user receives moves from client subscriptions into Sync Rules on the server.

Try it

The check has 2 inputs: the file text and a date. Paste a file into the web version or open it in VS Code; all 16 rules run on it with no key. The full version scans a whole workspace and writes one Markdown migration report for the team.