Multi AZ provides a mechanism to failover the RDS database to another synchronously replicated
copy in the event of the failure of an AZ.
There is no option for multiple region failover of Amazon RDS.
Read replicas are used for offloading read traffic from a primary database but cannot be used for
writing. You can failover the DB by promoting a read replica in a DR situation but this is not
the best answer as the multi-AZ feature is preferred.