One of the key benefits of using Kafka Streams over other streaming engines is that the stream processing apps / microservices don’t need a cluster. Rather, each microservice can be run as a standalone app (e.g: jvm container). You can then spin multiple instances of each to scale up the microservice. Kafka will treat this as a single consumer group with multiple instances. Kafka streams takes care of consumer partition reassignments for scalability.
You can see how to start these three microservices here.
If you’re trying to wrap your head around streaming apps, give this a try. George has all of the code in his GitHub repo.