AWS App Sync Migration Guide
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As of September 2024, Device Services is deprecated. There are many third-party services you can use to migrate your App Services app. This page provides guidance in using AWS AppSync.
What is AWS AppSync?
AWS AppSync is a serverless platform that you can use to keep your data synchronized between devices through GraphQL and Pub/Sub APIs. Combined with MongoDB Atlas as the backend datastore, you maintain many of the benefits of Device Sync.
System Architecture
Device Sync
The following diagram shows the typical Device Sync architecture:
In this architecture, your app uses the Atlas Device Sync APIs to communicate directly with Atlas App Services, which handles data storage, synchronization, and conflict resolution.
The data flow is:
Data is stored in each device’s local realm db.
A user makes changes on the device.
Device Sync APIs send changes to Atlas App Services.
Atlas App Services performs any necessary conflict resolution, stores the changes in Atlas, and syncs the changes to the other devices.
Device Sync APIs update the data in each device’s local realm.
AWS AppServices
When you migrate from Device Sync to AWS AppSync, you will need to make the following changes to your architecture:
Use AWS AppSync to handle data synchronization
Use an AWS Lambda Resolver to send data to Atlas via the MongoDB driver SDKs
Use AWS Event Bridge to listen for event triggers from Atlas
Add a Database Trigger to Atlas
You also need to change the following in your client code:
Because AppSync uses GraphQL, you need to use AWS AppSync APIs to access GraphQL endpoints from your application.
Change the local datastore from a Realm database to the default datastore on the device (typically SQLite), or another one of your choice.
The following diagram shows a typical example of the new architecture:
Migration Steps
The following sections outline the high-level tasks you need to perform to migrate your existing Device Sync architecture to AWS AppSync.
MongoDB Atlas
If needed, update the database security and network access.
Create a Database Trigger that fires an event whenever data in your database or collection changes.
AWS
EventBridge
Configure Atlas as the partner source.
Configure AWS AppSync as the target.
Create a mapping of the event body’s fields to AppSync’s GraphQL endpoints
Configure security
AWS Lambda Resolver
Create a Lambda resolver based on the
MongoDB-DataAPItemplate. For details on this process, refer to the Readme in the MongoDB-API GitHub repo.Configure Lambda authorization via IAM
AWS AppSync
Configure IAM permissions
Link to the Lambda Resolver, using Lambda authorization.
Create GraphQL schemas for your data.
Application Code
Once you have your backend architecture migrated, you need to make a few changes to your client app:
Replace the Realm SDKs with code to call the AppSync GraphQL endpoints. You can use your existing platform with the appropriate AWS SDKs, or use AWS Amplify, which provides native support for connecting to AWS services.
Add drivers to write and read from the device’s datastore. The default datastore is SQLite in both iOS and Android environments, but use the database that meets your needs.