Monitoring DynamoDB global tables

ReplicationLatency—The elapsed time between when an item is written to a replica table, and when that item appears in another replica in the global table. ReplicationLatency is expressed in milliseconds and is emitted for every source- and destination-Region pair.

During normal operation, ReplicationLatency should be fairly constant. An elevated value for ReplicationLatency could indicate that updates from one replica are not propagating to other replica tables in a timely manner. Over time, this could result in other replica tables falling behind because they no longer receive updates consistently. In this case, you should verify that the read capacity units (RCUs) and write capacity units (WCUs) are identical for each of the replica tables. In addition, when choosing WCU settings, follow the recommendations in Global tables version.

ReplicationLatency can increase if an AWS Region becomes degraded and you have a replica table in that Region. In this case, you can temporarily redirect your application's read and write activity to a different AWS Region.