CQRS stands for Command Query Responsibility Segregation. CQRS is a software architectural pattern that separates the operations that read data (queries) from the operations that modify data (commands) into different models.
- With CQRS, you have separate models for reads and writes, each optimized for its specific purpose.
- This separation allows you to scale and optimize each model independently, as they have different requirements.
- For example, the read model can be optimized for fast and efficient queries, while the write model can focus on ensuring data consistency and integrity.
What is Command?
A command represents an intention to change the state of the system. It encapsulates the necessary information to perform an action, such as creating a new record, updating an existing record, or deleting a record.
- Commands are typically imperative and result-oriented, meaning they specify what should be done rather than how it should be done.
- In CQRS, commands are used to perform write operations on the data model.
What is Query?
A query is a request for data retrieval. It specifies the data needed and any conditions or filters to be applied. Queries are typically declarative, meaning they specify what data is desired without specifying how to retrieve it. In CQRS, queries are used to perform read operations on the data model.
What is Responsibility?
In software design, responsibility refers to the concept of assigning specific tasks or functions to different parts of the system. In CQRS, responsibility is segregated between the command side and the query side.
- The command side is responsible for handling commands and updating the write model (the part of the system that stores data for write operations)/
- While the query side is responsible for handling queries and providing data from the read model (the part of the system that stores data for read operations).
What is Segregation?
Segregation refers to the act of separating or dividing into distinct parts. In CQRS, segregation is applied to separate the concerns of reading and writing data.
- By segregating these concerns, CQRS allows each part of the system to be optimized for its specific purpose.
- For example, the write model can be optimized for consistency and transactional integrity, while the read model can be optimized for performance and scalability.