Introduction to Event-Driven Architectures

Event-driven architecture (EDA) is the foundational design of an application’s communication of state changes around an asynchronous exchange of messages called events. The architecture allows applications to be developed as a highly distributed and loosely coupled organization of components. Probably predominantly, the most well-known arrangement of components today is the microservices architecture for applications.

Our world is made up of events—they’re happening everywhere around us. A simple act of waking up in the morning becomes an event the instant it occurs. The same goes for the act of purchasing a book. Whether or not it was recorded that way in some database, somewhere, it was considered an event. Since it has occurred, several other operations might have sprung from it.

Just as companies looked at microservices a decade ago to address issues such as web-scale, EDA is gaining in interest and proponents of continuing that journey to help with global-scale.

It is my goal in this chapter to introduce you to the concepts and components of EDA and its applications that we will be using to demonstrate what EDA has to offer. We’ll also be taking a grounded look at the benefits and reasons to use EDA and the challenges you’re likely to encounter when starting a new greenfield project or adding select concepts and components to an existing project.

Whether you’re looking to start a new project with an event-driven approach or looking to break up a monolithic application into modules or further into microservices, this book will give you the information and patterns necessary to implement EDA where you need it.

In this chapter, we’re going to cover the following main topics:

• An exchange of facts
• The MallBots application
• Benefits of EDA
• Challenges of EDA