Part 3

You’ll explore and learn the Kafka Streams DSL layer and fully appreciate what types of event-streaming applications you can create. You’ll start with a simple “Hello World” application in Kafka Streams. From there, you’ll quickly move on to a more practical example involving a fictional retail store. But you will continue there; from starting with the more straightforward DSL applications, you’ll move on to more features, such as using state in a Kafka Streams application. You’ll need to use state whenever you need to “remember” something from previous events. From there, the next stop on your learning journey is the KTable API, where a KStream is an event stream and a KTable is an update stream where records with the same key are updated to previous ones. Then, you’ll move on to a concept that goes hand in hand with stateful operations—windowing. Where stateful operations on their own will continue to grow in size over time, windowing allows you to put events into discrete time “buckets,” breaking the state up into more analyzable chunks by time.