More complex systems

More complex systems can be created where the events pass through multiple stages and are even designed for easy plugin systems working from the same queue.

This can create complicated setups where the data flows through complex pipelines and is processed by independent modules. These kinds of scenarios are typically seen on instrumentation that aims to analyze and process big quantities of data to try and detect patterns and behaviors.

Imagine, for example, a system that makes bookings for a travel agency. There are a lot of searches and bookings requests that happen in the system, with associated purchases such as car rentals, luggage bags, food, and so on. Each of the actions produces a regular response (search, book, purchase, and so on), but an event describing the action will be introduced into a queue to be processed in the background. Different modules will analyze user behavior with different objectives in mind.

For example, the following...