Spring Data Flow brings the microservices architecture into typical data flow and event flow scenarios. We will discuss more about these scenarios later in this chapter. Building on top of other Spring Projects, such as Spring Cloud Stream, Spring Integration, and Spring Boot, Spring Data Flow makes it easy to define and scale use cases involving data and event flows using message-based integration.

In this chapter, we will discuss the following topics:

• Why do we need asynchronous communication?
• What is Spring Cloud Stream? How does it build on top of Spring Integration?
• Why do we need Spring Data Flow?
• What are the important concepts in Spring Data Flow you would need to understand?
• What are the use cases where Spring Data Flow is useful?

We will also implement a simple event flow scenario with three microservices acting as the source (application generating the events), processor, and sink (application consuming events). We will implement the microservices using Spring Cloud Stream and establish connections between them over the message broker using Spring Cloud Data Flow.