How does Amazon RDS ensure high availability?

Amazon RDS ensures high availability primarily through Multi-AZ deployments. This feature allows users to create standby replicas of their databases in separate Availability Zones. When a Multi-AZ deployment is configured, RDS automatically replicates the database data synchronously to the standby instance. In the event of an outage, maintenance event, or failure of the primary database, Amazon RDS can automatically failover to the standby instance with minimal downtime. This setup effectively enhances the resilience and availability of the database, ensuring that applications can continue to function even in adverse conditions.

While automated backups and read replicas contribute to data durability and read scaling, respectively, they do not directly address high availability in the same way Multi-AZ deployments do. Automated backups protect against data loss but do not keep an active instance running in a different Availability Zone. Read replicas are primarily used for scaling read operations and do not provide failover capabilities or the ability to maintain high availability during a failure of the primary database instance. A distributed database architecture, while beneficial for certain use cases, is not how Amazon RDS achieves high availability. Thus, Multi-AZ deployments remain the central feature for ensuring that databases hosted on RDS are highly available.