Amazon Relational Database Service (Amazon RDS) now supports highly available configurations with Multi-AZ deployments for PostgreSQL and for MySQL on AWS Outposts in all commercial regions. Amazon RDS Multi-AZ on Outposts deployments provide enhanced availability and durability for RDS database (DB) instances, making them a natural fit for production database workloads. When you provision a Multi-AZ database instance, Amazon RDS automatically creates a primary DB Instance and synchronously replicates the data to a standby instance on a second AWS Outposts connected to a different Availability Zone (AZ). Each Outposts runs on its own physically distinct, independent infrastructure, and is engineered to be highly reliable. In case of an infrastructure failure, Amazon RDS performs an automatic fail-over to the standby, so that you can resume database operations as soon as the fail-over is complete.
Source:: Amazon AWS