Scala Reactive Programming

The CQRS pattern

CQRS stands for Command Query Responsibility Segregation. CQRS is an architectural pattern created by Greg Young, based on Bertrand Meyer's Command and Query Separation principle.

Greg Young, the father of CQRS, coined this term. The CQRS pattern was inspired by the Command Query Separation (CQS) technique.

Wikipedia defines this CQS as follows:

It states that every method should either be a command that performs an action, or a query that returns data to the caller, but not both. In other words, asking a question should not change the answer. More formally, methods should return a value only if they are referentially transparent and hence possess no side effects.

We know that every system or application has two kinds of ...