Implement Command Query Responsibility Segregation for scalable architectures. Use when separating read and write models, optimizing query performance, or building event-sourced systems.

CQRS Implementation Comprehensive guide to implementing CQRS (Command Query Responsibility Segregation) patterns. When to Use This Skill Separating read and write concerns Scaling reads independently from writes Building event sourced systems Optimizing complex query scenarios Different read/write data models needed High performance reporting requirements Core Concepts 1. CQRS Architecture 2. Key Components Component Responsibility Command Intent to change state Command Handler Validates and executes commands Event Record of state change Query Request for data Query Handler Retrieves data from read model Projector Updates read model from events Templates and detailed worked examples Full template library and detailed worked examples live in references/details.md . Read that file when you need the concrete templates. Best Practices Do's Separate command and query models Different needs Use eventual consistency Accept propagation delay Validate in command handlers Before state change Denormalize read models Optimize for queries Version your events For schema evolution Don'ts Don't query in commands Use only for writes Don't couple read/write schemas Independent evolution Don't over engineer Start simple Don't ignore consistency SLAs Define acceptable lag

cqrs-implementation