Open Search Cross Cluster Replication

Understanding Active Passive Cross Cluster replication for AWS Open Search1 is pretty straightforward. You have a leader index in the active cluster that replicates everything to the follower index in the passive cluster. In case there is a DR and we witness a region failure, we can continue to process read operations through the follower index on the passive cluster.

However, the documentation provided does not go through the following two points.

1. How do we handle write operations that come during the time the active cluster is down. Is it possible to write on the passive cluster during this time and the primary would catch up when it comes back online or only read is possible during this time, and we need to batch process all the writes once active cluster comes back up ?

2. When active cluster comes back online, does Open Search automatically starts redirecting search queries back to active cluster instead of the passive cluster ?

3. In addition, in case we wish to test the DR failover setup for Open Search, is it possible to simulate active cluster failure and test ?

1 https://docs.aws.amazon.com/opensearch-service/latest/developerguide/replication.html