Amazon Relational Database Service (Amazon RDS) for MySQL now supports inbound replication from Amazon RDS Single-AZ database (DB) instances and Amazon RDS Multi-AZ DB instances with one standby to Amazon RDS Multi-AZ deployments with two readable standby database (DB) instances. You can use this inbound replication to help migrate your existing Amazon RDS MySQL deployments within minutes to Amazon RDS Multi-AZ deployments with two readable standby db instances, which has one writer instance and two readable standby instances across three availability zones. By creating a Multi-AZ deployment with two readable standby db instances as a read replica of your existing RDS MySQL database instance, you can promote the read replica to be your new primary, typically within minutes.
Source:: Amazon AWS