CQRS Without the Complexity
17 days ago
- #CQRS
- #Software Architecture
- #Event Sourcing
- CQRS (Command Query Responsibility Segregation) separates the responsibility of changing state (Commands) from reading state (Queries).
- Commands express an intention to change the system state, while Events record what has already happened as immutable facts.
- Subjects (or Streams) organize events related to a specific entity (e.g., a book) under a unique identifier.
- Event Sourcing stores events as the primary source of truth, allowing the system to reconstruct current state by replaying events.
- Projections build specialized Read Models from event streams, optimized for specific queries like available books or member statistics.
- CQRS provides flexibility, scalability, and simplicity by allowing read and write models to evolve independently.
- Eventual consistency means there's a small delay between a command succeeding and read models reflecting the change, which is usually not problematic.
- Starting with CQRS can be simple: identify an area with different read/write needs, use commands and events, and build one projection.
- Frameworks like OpenCQRS can help implement CQRS patterns without building everything from scratch.
- CQRS and Event Sourcing together make explicit the separation of concerns and optimization of different operations in a system.