The concepts of Multi-AZ and Read Replicas apply to Amazon Aurora as well, but with some key differences and additional considerations due to Aurora’s unique architecture:

Multi-AZ Deployments (High Availability):

• Purpose: Same as with other RDS engines, Multi-AZ deployments in Aurora are primarily for high availability and disaster recovery.
• How it Works: Aurora automatically replicates your data across three Availability Zones (AZs) within a region. Each AZ has a copy of your data, and Aurora can automatically failover to another AZ if there’s an issue with the primary AZ.
• Benefits:
  • Enhanced Availability: With data stored across three AZs, Aurora is highly resilient to infrastructure failures.
  • Automatic Failover: Aurora automatically handles failover, ensuring minimal downtime.
  • No Performance Impact: The standby replicas do not handle read traffic, so there’s no performance impact on the primary instance.
• Limitations:
  • Not for Read Scaling: Multi-AZ does not provide read scaling, as the standby replicas are not used for read traffic.
  • Cost: Multi-AZ deployments are more expensive than single-AZ deployments.

Read Replicas (Read Scalability):

• Purpose: Read replicas in Aurora are used for read scaling, offloading read traffic from the primary instance.
• How it Works: You can create up to 15 read replicas across multiple AZs within a region, or even across different regions. Aurora replicates data asynchronously to the read replicas.
• Benefits:
  • Read Scaling: Distribute read traffic across multiple replicas to handle high read workloads.
  • Global Read Replicas: Create read replicas in different regions for global read scalability and reduced latency.
  • Disaster Recovery: Read replicas can be promoted to primary instances in case of a disaster.
• Limitations:
  • Replication Lag: There may be a slight replication lag between the primary instance and read replicas.
  • Cost: Read replicas incur additional costs.

Choosing Between Multi-AZ and Read Replicas:

• High Availability: If high availability is your primary concern, then choose a Multi-AZ deployment. Aurora’s built-in replication across three AZs provides excellent protection against infrastructure failures.
• Read Scalability: If read scaling is your primary concern, then choose Read Replicas. You can create multiple read replicas to handle high read traffic and distribute it across different AZs or regions.
• Both: You can combine Multi-AZ deployments with Read Replicas to achieve both high availability and read scalability. This provides a robust solution for critical applications with demanding read workloads.

Additional Considerations for Aurora:

• Aurora Serverless: Consider using Aurora Serverless if you have unpredictable workloads. It automatically scales capacity up or down based on demand.
• Global Database: Aurora Global Database allows you to create a multi-region Aurora deployment for global read scaling and disaster recovery.