A new tutorial demonstrates bi-directional data synchronization between local ObjectBox databases and a MongoDB Atlas cluster. Developers can build offline-first applications that sync seamlessly across Android and iOS devices. The guide walks through configuring the ObjectBox Sync Server and its MongoDB Sync Connector to handle real-time data streaming and conflict resolution.

The architecture centers on the Sync Server, which manages connections and queues data changes. A Java client app performs CRUD operations locally, with changes pushed to MongoDB and updates flowing back. The tutorial specifies using Docker Compose for deployment and requires a MongoDB replica set instance, with version 8.0 recommended for the connector.

Developers will learn to run an initial full sync from MongoDB and verify two-way synchronization. The system is designed for production use, allowing teams to swap in their own data models. This setup provides a practical solution for maintaining data consistency in applications where offline functionality is critical.