This guide provides a comprehensive roadmap for migrating from MongoDB Atlas Device Sync to Ditto. By making this transition, you’ll benefit from resilient data synchronization, offline-first capabilities, and efficient data management for a consistent user experience in any environment.

Why Ditto?

Ditto offers a decentralized solution for faster, more efficient data synchronization at the edge. Unlike traditional cloud-based systems, Ditto provides an offline-first architecture that ensures your app continues to operate smoothly even when internet connectivity is limited or unavailable. We take offline functionality one step further by utilizing peer-to-peer synchronization and mesh networking. These core capabilities enable your applications to not just operate smoothly in any network environment but sync in real-time without reliance on WiFi, servers, or the cloud.

With just your existing mobile and edge devices, Ditto unlocks,

Please review this guide thoroughly to understand the necessary requirements and changes. By following the outlined steps, your team can successfully migrate to a more robust solution with minimal disruptions.

If you need further assistance at any point, feel free to reach out to our support team.

Ditto works across a wide range of platforms, programming languages, and device types, allowing for flexible real-time syncing in many environments. Whether you’re building for iOS, Android, or desktop environments, or integrating across devices using different transport methods like Bluetooth or Wi-Fi, Ditto supports it.

Before migrating, it’s important to review the Compatibility Guide to ensure you’re familiar with all the platforms and languages we support. This will help you understand the various options available for your project and ensure your app can take full advantage of Ditto’s peer-to-peer capabilities.

Explore our Compatibility Guides →

Ditto lets your apps sync directly between clients (Small Peers) and a Big Peer (Cloud Platform) for real-time data sharing, with an offline-first design. This setup reduces the need for constant cloud access and improves performance.

This guide will help you replace Realm on the client side to start using Ditto’s peer-to-peer syncing right away. The integration between Ditto's Big Peer and MongoDB is enabled by the MongoDB connector, which synchronizes data bi-directionally between Ditto and MongoDB.

Unlike other data synchronization systems for MongoDB, Ditto's advanced conflict resolution (based on CRDTs) avoids the need to deploy extra backend services to handle writes and conflicts, just deploy a Big Peer and you have everything you need to integrate with MongoDB.

You can sign up for the MongoDB Connector waitlist to request access to the preview!

To get started with Ditto, sign up for an account and create a new project in the Ditto dashboard. You’ll need to grab your API keys to integrate Ditto with your app for real-time syncing.

Before adding Ditto, we advise you remove MongoDB Realm from your project. This includes uninstalling the Realm SDK and clearing out any Realm-related code and dependencies. Removing Realm at this stage will let you identify all parts of your codebase touching Realm that will need to be migrated to Ditto with the compiler. It is also possible to postpone this until later in the process, and effectively run Realm and Ditto in parallel, if desired.

Now that Realm is removed, it’s time to install Ditto. Follow our installation guides to add Ditto to your project. Be sure to configure the right permissions for your app, like background mode and local network access.

Next, you’ll set up Ditto in your app by initializing the Ditto service with your API keys. This will allow your app to start syncing data between devices using Ditto’s real-time peer-to-peer capabilities.

Ditto is distributed by default, meaning it will automatically connect to, and sync data across your nearby devices. In order to solely rely on device-to-cloud sync, you can disable local sync by turning off LAN, peer-to-peer Wi-Fi, and Bluetooth transports.

With Realm your models are tightly coupled to Realm’s classes. This is not required with Ditto.

Make sure to review your data types, relationships, and primary keys, and update them where necessary to work seamlessly with Ditto’s peer-to-peer sync architecture.

Before (Realm model):

After (Ditto model):

There are a few conventions with Ditto data models worth considering:

We also recommend you make yourself familiar with REGISTER, MAP, and ATTACHMENT data types. Read more about best practices for data modelling with Ditto in this guide.

You can replace Realm's sync logic with Ditto subscriptions to keep data in sync between your devices in real-time.

Now, update the create, read, update, and delete (CRUD) operations in your app. Replace Realm’s methods with Ditto’s, ensuring all your data interactions are using Ditto’s sync logic.

When adding new items, use the execute method on the ditto.store object to insert your data. This ensures new records are synced efficiently across peers in real-time.

Refactor how you retrieve data by leveraging Ditto’s powerful observation capabilities.

When reading data in Ditto, the primary method is to set up an observer that listens for changes and updates in real-time. This ensures your app automatically reflects the latest data from other peers.

Real-Time Observing

This allows your app to respond to data changes in real-time by syncing updates across all connected devices.

One-Off Reads

In addition to real-time observations, Ditto allows for one-time reads. These are useful when you need to fetch data at a specific point in time without continuously listening for updates. You can do this by using the execute method on the ditto.store using the same query (for example: “SELECT * FROM todos WHERE isDeleted = false”)

When updating data, use UPDATE on the ditto.store object. Ditto lets you sync the minimum data needed, ensuring that all peers converge on the same version of the data across the network.



In a distributed data system like Ditto, deletion follows a “soft delete” pattern. This means that when you mark an item as deleted, it’s not immediately removed from the collection or local storage. Instead, the item is flagged as deleted to ensure that other devices in the network remain in sync. To fully remove the item and free up space, you’ll need to evict these “soft deleted” items. For more details, see the section on Evictions.

Your app needs to react to changes in real-time data. Set up observers to make sure your UI updates when the data synced through Ditto changes.

In distributed systems, it’s important to manage storage efficiently, especially when dealing with large datasets or limited device space. Evictions allow you to remove data that is no longer needed, freeing up space in a controlled way while maintaining the integrity of your app’s data.

To manage storage, Ditto allows you to configure eviction policies. This lets you free up space by removing data that is no longer needed or marked as deleted (as described in the soft delete section).

For more on evictions and deletion, refer to Ditto’s documentation: Evictions and Delete.

A production application must have robust auth system in place. Ditto lets you rebuild your Atlas Device Sync authentication and authorization flow in this document: Migrating Authentication and Authorization from Atlas Device Sync to Ditto