Command Query Responsibility Segregation (CQRS)

Intent

Separate the write model (commands) from the read model (queries) so each can evolve and scale independently.

Use when

• Read and write workloads differ significantly (shape, scale, latency).
• You need denormalized read models or multiple projections optimized for different queries.

Avoid / watch-outs

• CQRS adds complexity; avoid for simple CRUD when a single model works.
• Be explicit about consistency (staleness) and user-visible semantics.

Skill mapping

• architecture: decide if CQRS is warranted and define projection ownership.
• spec: acceptance criteria for eventual consistency and read-your-writes expectations.
• observability: projection lag and rebuild visibility.
• testing: tests that pin behavior under staleness and rebuild scenarios.