The Command Query Responsibility Segregation (CQRS) Pattern

The Command Query Responsibility Segregation (CQRS) pattern is a software design pattern that separates an application's read and writes operations into separate models. It was first introduced by Greg Young as a way to address some common challenges in complex and scalable applications.

The main idea behind CQRS is to separate the write operations (commands) from the read operations (queries) and treat them differently. Therefore, the pattern introduces two distinct models: the Command and Query models.

• Command Model: The Command model manages to write operations by capturing the intention to modify the system's state and converting it into commands. The model processes these commands, which update the relevant data in the system while enforcing business rules, performing validations, and handling transactional aspects.
• Query Model: The Query model efficiently handles all read operations and ensures optimized data structures and query mechanisms for efficient data fetching. It denormalizes data to enhance read performance and tailors it to suit various read scenarios like search, reporting, or analytical queries. The model can be optimized for different types of queries.

By separating the read and write operations, CQRS allows each model to be independently optimized for its specific requirements.

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