CQRS Pattern — Architecture Patterns

The Command Query Responsibility Segregation (CQRS) pattern is a software architecture pattern that separates the responsibility of commands(write operations) and queries(read operations) into two separate models. It emphasizes the idea that the operations to retrieve data (queries) should be treated differently from the operations that modify data (commands).

By separating the read and write responsibilities, CQRS enables more flexibility and scalability in system design. It allows the read-and-write models to be scaled independently, as they often have different performance characteristics. Let’s understand this with an example!

CQRS Pattern

Let’s assume we’re building an e-commerce application. The e-commerce application has two main types of operations:

  • Commands: These are operations that change the state of the data, such as placing an order or adding a product to a shopping cart.
  • Queries: These are operations that retrieve data from the system, such as displaying a list of products or showing the order history for a customer.

The CQRS pattern can be used to separate these two types of operations into two separate models:

  • The write model: This model stores the current state of the data. It is used to execute commands and to ensure that the data is always consistent.
  • The read model: This model is used to retrieve data from the system. It is optimized for speed and performance, and it may not always be up-to-date with the write model.

In this example, the write model would be stored in a relational database, such as MySQL or PostgreSQL. The read model could be stored in a NoSQL database, such as MongoDB or Cassandra. This architecture would allow the e-commerce application to improve its performance and scalability, both from a read & write perspective.

CQRS Sample Implementation

Advantages of CQRS Pattern

  1. Scalability: CQRS pattern allows you to scale the read and write sides of your application independently. By separating the read and write models, you can optimize each model for its specific use case. This can result in significant performance improvements, especially for applications that require high…
Pratik Pandey - https://pratikpandey.substack.com

Senior Engineer with experience in designing and architecting large scale distributed systems.