Overview

In Amazon RDS, you can improve availability and performance using two core mechanisms:

1. Multi-AZ Deployments → High Availability (HA) and automatic failover
2. Read Replicas → Performance scaling for read-heavy workloads

Both sound similar — but they serve different purposes.

This guide breaks down the difference, how they work, and when kaptaindevops should use each.

Multi-AZ Deployments

What It Is

Multi-AZ (Multi-Availability Zone) provides high availability and failover protection for your RDS instance.

When you enable Multi-AZ:

• AWS automatically creates a synchronous standby replica in a different Availability Zone.
• Writes are synchronously replicated to the standby.
• In case of instance or AZ failure, automatic failover occurs within seconds.

Architecture

Clients connect via a single DB endpoint — AWS automatically redirects it to the standby during failover.

Key Features

• Automatic failover on hardware/instance/AZ failure
• Synchronous replication (zero data loss)