RDS Multi-AZ vs Read Replicas

Learn the differences between Multi-AZ deployments and Read Replicas, when to use each, and how to combine them.

rds-ha-config.json
{
"MultiAZ": true,
"AvailabilityZone": "us-east-1a",
"ReadReplica": false
}
rds-ha-config.json
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Tutor:RDS provides two main options for high availability and read scaling: Multi-AZ deployments and Read Replicas. Understanding the differences is crucial for designing resilient database architectures.


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RDS provides two main options for high availability and read scaling: Multi-AZ deployments and Read Replicas. Understanding the differences is crucial for designing resilient database architectures.

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RDS Multi-AZ vs. Read Replicas

Author

Pascual Vila

Cloud Instructor.

RDS provides two main options for high availability and read scaling: Multi-AZ deployments and Read Replicas. Understanding the differences is crucial for designing resilient database architectures.

Multi-AZ Deployments

Multi-AZ deployments provide high availability and data durability. RDS automatically creates and maintains a synchronous standby replica in a different Availability Zone. If the primary instance fails, RDS automatically fails over to the standby.

Read Replicas

Read Replicas are read-only copies of your database instance. They can be in the same or different Availability Zones, or even in different regions. Read replicas improve read performance and can be promoted to become standalone instances.

Key Differences

Multi-AZ is for high availability with automatic failover, while Read Replicas are for read scaling. Multi-AZ uses synchronous replication, while Read Replicas use asynchronous replication. You can combine both for maximum resilience and performance.

RDS HA Glossary

Multi-AZ Deployment
A high availability configuration where RDS automatically creates and maintains a synchronous standby replica in a different Availability Zone. Provides automatic failover if the primary instance fails.
Read Replica
A read-only copy of your database instance. Read replicas can improve read performance and can be promoted to become standalone database instances. Uses asynchronous replication.
Synchronous Replication
Data is written to both the primary and standby instances simultaneously. Used in Multi-AZ deployments to ensure zero data loss during failover.
Asynchronous Replication
Data is written to the primary instance first, then replicated to the replica. Used in Read Replicas. There may be a slight delay (lag) between primary and replica.
Automatic Failover
The process of automatically switching from a failed primary instance to a standby instance. In Multi-AZ deployments, failover typically takes 60-120 seconds and is transparent to applications.