CQRS

Definitions

1. Command Query Responsibility Segregation — separating read and write operations into different models. Writes go to one optimized store; reads come from another. Adds complexity but solves performance problems at scale.

   In plain English: Splitting your system into two separate paths — one optimized for saving data and another optimized for reading it — because the best way to write data and the best way to display it are often very different.

2. CQRS is often paired with Event Sourcing, where state changes are stored as a sequence of events rather than overwriting current state. Together they enable powerful patterns like temporal queries and audit logs, but the complexity cost means they're only justified at significant scale.

   Example: 'We implemented CQRS for the order system — writes go to a normalized PostgreSQL database, reads come from a denormalized Elasticsearch index optimized for search.'

   Source: Event Sourcing pairing

Related Terms

• Message Queue
• Event-Driven Architecture
• Eventual Consistency
• MVVM
• Onion Architecture
• Platform Abstraction
• Threading Model
• Triple