# Read Replica

Record: `arch:read-replica`
Kind: technique
Layer: [Performance Core](https://banes-lab.com/records/layer/performance-core.md)
Severity: contextual
Scope: service, database, scalability
Canonical: https://banes-lab.com/ontology#arch-read-replica

## Repair

- Refactored by: Route Reads to Replicas
- Detected by: read load saturating the write primary
- Violated by: all reads and writes hitting one primary
- Measured by: primary read/write contention ratio
- Enforced by: database design review

## requires

- [Replication](https://banes-lab.com/records/arch/replication.md)

## reinforces

- [Horizontal Scaling](https://banes-lab.com/records/arch/horizontal-scaling.md)
- [Load Balancing](https://banes-lab.com/records/arch/load-balancing.md)

## enables

- [Read Traffic Offload](https://banes-lab.com/records/lex/read-traffic-offload.md)

## conflicts-with

- [Single-Primary Read Contention](https://banes-lab.com/records/lex/single-primary-read-contention.md)

## tensions-with

- [Read-Your-Writes Consistency](https://banes-lab.com/records/lex/read-your-writes-consistency.md)

## tensions

- [Read Replica Read-Your-Writes Consistency](https://banes-lab.com/records/tension/read-replica-read-your-writes-consistency.md)