Using DynamoDB sync operations on versioned data sources in AWS AppSync
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, aScan
on the Base table is performed. -
If the
lastSync
field is specified, but the value is before thecurrent moment - DeltaSyncTTL
, aScan
on the Base table is performed. -
If the
lastSync
field is specified, and the value is on or after thecurrent moment - DeltaSyncTTL
, aQuery
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.