Read Replica

Kind: technique

Layer: Performance Core

Record: architecture:read-replica

Severity: contextual

Scope: service, database, scalability

Canonical: Ontology

A technique for routing read queries to replicated copies of a database, so the primary handles only writes.

Listed in Architecture principles, after CDN / Edge Caching and before Queuing Theory.

Requires

• Replication

Reinforces

• Horizontal Scaling
• Load Balancing

Enables

• Read Traffic Offload

Conflicts with

• Single-Primary Read Contention

In tension with

• Read-Your-Writes Consistency

Tensions

• Read Replica / Read-Your-Writes Consistency

Violated by

• Single-Primary Read Contention

Severity

• contextual

Category

• Scalability / Performance / Optimization

Refactors

• Failover
• Redundancy

Linked from

• Scalability / Performance / Optimization
• Self-Healing / Recovery / Deployment Safety
• Scalability / Performance / Optimization
• Severity levels
• The resolutions