Diving into event-driven and reactive approaches

Event-driven architecture isn't a new concept. My first experiences with it were related to GUI development (with Java Swing) a long time ago. But, of course, the concept is older than that. And the reason is that events, meaning things that happen, are a pretty natural phenomenon in the real world.

There is also a technological reason for the event-driven approach. This way of programming is deeply related to (or in other words, is most advantageous when used together with) asynchronous and non-blocking approaches, and these paradigms are inherently efficient in terms of the use of resources.

Here is a diagram representing the event-driven approach:

Figure 6.5 – Event-driven approach

As shown in the previous diagram, the whole concept of the event-driven approach is to have our application architecture react to external events. When it comes to GUIs, such events are mostly user inputs (such...