Amazon RDS on VMware Adds Support for Cross-Custom-Availability-Zone Read Replicas
To provide enhanced performance and read scalability, Amazon RDS on VMware adds support for read replicas across Custom Availability Zones for MySQL and PostgreSQL databases. You can create cross-custom-availability-zone read replicas of a DB instance to serve read traffic in one region, thereby increasing aggregate read throughput. A read replica can also be promoted to become a standalone DB instance if the source DB instance fails.
Source:: Amazon AWS