With RDS Custom for SQL Server, what will be preserved after a failover and how long does failover take?

Please note that RDS Custom for SQL Server has slight differences between RDS SQL Server. In RDS Custom for SQL Server, failover takes 60-120 seconds. Block-level, synchronous replication is used. (That means, when the disk is confirmed as written on the primary, it has been written on the 2ndary.) When failing over: (1) you will lose the hot memory cache. (2) if you have long-running transactions that are not yet committed and a failover occurs, they will roll back.

Please note that this answer is current as of July 2023. Be sure to check documentation for any updates.