Earlier in this chapter we have seen the motivations and concepts behind event sourcing, event-driven architectures, and CQRS. CQRS offers an interesting approach to creating distributed applications that implement scalable, eventually consistent business use cases.

At the time of writing, there is a lot of interest in CQRS, yet little knowledge within companies of how to use it. Some frameworks and technologies have emerged that aim to implement this approach. Yet CQRS is an architectural style, and specific frameworks are not necessary to develop CQRS systems.

Let's have a close look at an approach that uses Java EE.