Design Patterns for Cloud Native Applications

Chapter 5. Event-Driven Architecture Patterns

Event-driven architecture is a software architecture paradigm that promotes generation, detection, consumption, and reaction based on events. An event-driven architecture allows us to build distributed and scalable cloud native applications. In contrast to the service composition patterns, which are mostly synchronous in nature, event-driven architectures are asynchronous. They provide a clean and decoupled way of designing cloud native applications, allowing simpler scaling, and are one of the fundamental architectures for building large-scale distributed cloud native applications.

Events are used for sharing information. In most cases, the application generating the event notification does not expect any response, and it lets the consuming application decide what to do with that information. Even if the applications generating the event notification expect a response, they expect it only indirectly.

Note

Events can be categorized as any significant occurrence or change in a system state. Let’s take an example of depositing $50 into Bob’s account. Now, Bob’s account balance has increased by $50; this incident is considered an event. The occurrence of this event can be sent to other systems, such as to Bob’s cell phone, as a notification. The event notification is typically an asynchronous message produced and transmitted with the event occurrence information. Though events just occur and do not travel, the term event is also used ...