Can you explain the concept of CQRS and how it is applied in system architecture?

CQRS (Command Query Responsibility Segregation) is an architectural pattern that separates operations that change state (Commands) from data reading operations (Queries) into different models.

The main idea:

• Commands modify the system's state without returning data.
• Queries return data without changing the state.

This allows optimizing each part separately: for example, using cached or denormalized data for reading, and complex business logic for writing.

Example of application:

• In an order system, a Command handles creating and modifying orders.
• A separate Query provides quick access to order information for display to the user.

This approach improves scalability and simplifies the maintenance of complex systems.