Monitoring global tables

You can use Amazon CloudWatch to monitor the behavior and performance of a global table. Amazon DynamoDB publishes ReplicationLatency metric for each replica in the global table.

• 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.

For more information, see DynamoDB Metrics and dimensions.