Fundamentals of Software Architecture

Chapter 14. Event-Driven Architecture Style

The event-driven architecture style is a popular distributed asynchronous architecture style used to produce highly scalable and high-performance applications. It is also highly adaptable and can be used for small applications and as well as large, complex ones. Event-driven architecture is made up of decoupled event processing components that asynchronously receive and process events. It can be used as a standalone architecture style or embedded within other architecture styles (such as an event-driven microservices architecture).

Most applications follow what is called a request-based model (illustrated in Figure 14-1). In this model, requests made to the system to perform some sort of action are send to a request orchestrator. The request orchestrator is typically a user interface, but it can also be implemented through an API layer or enterprise service bus. The role of the request orchestrator is to deterministically and synchronously direct the request to various request processors. The request processors handle the request, either retrieving or updating information in a database.

A good example of the request-based model is a request from a customer to retrieve their order history for the past six months. Retrieving order history information is a data-driven, deterministic request made to the system for data within a specific context, not an event happening that the system must react to.

An event-based model, on the other hand, ...