What is CQRS (Command Query Responsibility Segregation)?
CQRS separates the read model (queries) from the write model (commands) into distinct data stores optimized for each purpose.
CQRS separates the read model (queries) from the write model (commands) into distinct data stores optimized for each purpose. Writes go to a normalized, consistent store. Reads come from denormalized, fast-query optimized stores. Events synchronize the two.
Benefits: Read and write stores can be independently scaled, each store can be optimized for its use case (normalized for writes, denormalized for reads), enables different consistency models (strong consistency for writes, eventual for reads).
CQRS is often paired with event sourcing: commands produce domain events (write side), events are projected into read-optimized views (read side). This combination enables auditability, scalability, and flexibility.
Why It Matters
CQRS solves the impedance mismatch between write requirements (data integrity, validation) and read requirements (speed, flexible queries). It enables independent scaling of reads and writes.
Frequently Asked Questions
What is CQRS?
Separating the read model from the write model into different stores. Writes use a normalized, consistent store. Reads use denormalized, query-optimized stores. Events synchronize both.
When is CQRS appropriate?
When read and write patterns differ significantly (many more reads than writes, or vice versa), when you need independent scaling, or when combined with event sourcing. Not for simple CRUD applications.
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