AWS Amplify JavaScript Library

DataStore uses different storage adapters depending on the environment (Web, Mobile, or SSR).

• Web: Uses IndexedDB.
• Mobile (React Native): Uses Async Storage (with an option to use SQLite).
• SSR (Server-Side Rendering): Uses InMemoryStore.

Note: The SQLite adapter is maintained in its own dedicated package: datastore-storage-adapter.

DataStore uses two primary synchronization methods to keep local data in sync with AppSync:

• Full Sync: Performed the first time DataStore is started on a new client. It fetches all records from AppSync.
• Delta Sync: Performed during subsequent app reloads (browser refreshes or new sessions). It fetches only the records that have changed after a specific timestamp.

Note on Sync Frequency: If the time elapsed since the last full sync exceeds the fullSyncInterval (which is configurable), DataStore will trigger a Full Sync instead of a Delta Sync.

The DataStore local database is organized into several namespaces that categorize the data stored on the device:

• datastore: Contains configuration and settings, such as schema versioning.
• user: Contains the actual application data records derived from your user-defined schema.
• sync: Contains internal metadata used by the Sync Engine to manage synchronization state.
• storage: (Deprecated)

Note: Any table name prepended with sync_ is an internal table used by the engine.

The Merger class ensures data consistency by preventing incoming remote changes from overwriting pending local changes.

Behavior:

• When a change arrives via a mutation response or an AppSync subscription, the Merger checks the local Outbox (mutation queue) for that specific record ID.
• If a pending mutation exists for that record: The incoming remote change is discarded and not saved to the local database. This prevents the client from temporarily undoing its own local changes.
• If no pending mutation exists: The incoming model is persisted to the local store via Storage.save.

Important Requirement: For the merge logic to function correctly, AppSync must be configured to send only updated fields in mutation responses.

AWS Amplify has undergone significant version changes.

• v6.x.x: The current major version. If you are upgrading from v5, refer to the official migration guide.
• v5.x.x: Actively supported.
• v4.x.x and below: Deprecated. These versions entered Maintenance Mode and will end all support on April 13, 2026. During Maintenance Mode, they only receive critical bug fixes and security updates. It is strongly recommended to upgrade to v6 as soon as possible.

Several Storage methods changed in version 5.x.x:

Storage.list

The maxKeys parameter was renamed to pageSize, and the return type now contains a results list.

- const photos = await Storage.list('photos/', { maxKeys: 100 });
- const { key } = photos[0];
+ const photos = await Storage.list('photos/', { pageSize: 100 });
+ const { key } = photos.results[0];

Storage.put (Resumable)

When resumable: true is used, the returned key no longer includes the bucket name.

- let uploadedObjectKey;
- Storage.put(file.name, file, {
-   resumable: true,
-   // Necessary to parse the bucket name out to work with the key
-   completeCallback: (obj) => uploadedObjectKey = obj.key.substring( obj.key.indexOf("/") + 1 )
- }
+ let uploadedObjectKey;
+ Storage.put(file.name, file, {
+   resumable: true,
+   completeCallback: (obj) => uploadedObjectKey = obj.key
+ }