What is CQRS?

CQRS (Command Query Responsibility Segregation) is an architectural pattern that separates read (Query) and write (Command) operations on data into different models.

Main idea:

• Commands change the system's state (create, update, delete).
• Queries return data without changing the state.

Advantages of CQRS:

• Allows optimizing data models for different tasks: normalized for writes, denormalized for reads.
• Simplifies scaling: reading and writing can be scaled independently.
• Improves support for complex business logic when changing data.

An example of a simplified structure in Go:

// Command — change of state
func CreateUserCommand(user User) error {
    // logic for creating a user
    return nil
}

// Query — data retrieval
func GetUserQuery(userID string) (User, error) {
    // logic for retrieving a user
    return User{}, nil
}

CQRS is often used together with Event Sourcing to manage state in distributed systems.