# Core concepts

## Overview

While you might have used REST as your service communications layer in the past, more and more projects are moving to an event-driven architecture. When a service performs some piece of work that other services might be interested in, that service produces an *event* — a record of the performed action. Other services consume those events so that they can perform any of their own tasks needed as a result of the event.

Since version 3.0, event-based communication is the framework prime focus of interest. It defines a uniform interface for asynchronous processing of incoming events. The mental model is very similar to other popular libraries that you can find in the frontend, like — `redux-observable` or `ngrx/effects`. Both libraries had a huge influence on design and architectural decisions. 

Messaging module can be applied to variety of models, including the post popular: queue, "pub/sub"-based [microservice](https://marblejs.gitbook.io/docs/messaging/microservices) communication, [CQRS](https://marblejs.gitbook.io/docs/messaging/cqrs) or EventSourcing.

{% content-ref url="microservices" %}
[microservices](https://marblejs.gitbook.io/docs/messaging/microservices)
{% endcontent-ref %}

{% content-ref url="cqrs" %}
[cqrs](https://marblejs.gitbook.io/docs/messaging/cqrs)
{% endcontent-ref %}

{% content-ref url="websockets" %}
[websockets](https://marblejs.gitbook.io/docs/messaging/websockets)
{% endcontent-ref %}