Sync operations

Versioned data sources support Sync operations that allow you to retrieve all the results from a DynamoDB table and then receive only the data altered since your last query (the delta updates). When AWS AppSync receives a request for a Sync operation, it uses the fields specified in the request to determine if the Base table or the Delta table should be accessed.

• If the lastSync field is not specified, a Scan on the Base table is performed.

• If the lastSync field is specified, but the value is before the current moment - DeltaSyncTTL, a Scan on the Base table is performed.

• If the lastSync field is specified, and the value is on or after the current moment - DeltaSyncTTL, a Query on the Delta table is performed.

AWS AppSync returns the startedAt field to the response mapping template for all Sync operations. The startedAt field is the moment, in epoch milliseconds, when the Sync operation started that you can store locally and use in another request. If a pagination token was included in the request, this value will be the same as the one returned by the request for the first page of results.

For information about the format for Sync mapping templates, see the mapping template reference.