CQRS Pattern
Separate read and write operations to optimize performance and scalability by using different data models for different operations.
Pattern Overview
Command Query Responsibility Segregation (CQRS) is a pattern that separates the read and write operations for a data store, allowing you to optimize each operation independently. Commands change the state of the system, while queries retrieve data without changing the system state.
When to Use
- • High-performance read operations
- • Complex business logic in commands
- • Different read and write requirements
- • Event sourcing implementations
When Not to Use
- • Simple CRUD applications
- • When consistency is critical
- • Small teams or simple domains
- • Real-time data requirements
System Architecture
CQRS separates the command side (write operations) from the query side (read operations), allowing each to be optimized independently with different data models and storage strategies.
Command Flow
Commands flow through the write side of the system, updating the domain model and generating events that eventually update the read models for eventual consistency.
Query Flow
Queries are handled by the read side, which can be optimized for specific query patterns and can use different data models optimized for reading.
Data Model
The data model shows how commands, events, and read models are structured and related in a CQRS system.
Benefits
- Optimized read and write performance
- Independent scaling of operations
- Flexible data models
- Better separation of concerns
Trade-offs
- Increased system complexity
- Eventual consistency challenges
- Data synchronization overhead
- Learning curve for developers