Using several example microservice applications, I'll compare and contrast using Akka Streams and Kafka Streams for stream processing with Kafka as the data "backplane". I'll discuss the strengths and weaknesses of each tool for particular design needs, so you'll feel better informed when making choices. I'll also contrast them with Spark Streaming and Flink, including when to chose them instead. For example, Akka and Kafka Streams are applications you embed in your microservices, while Spark and Flink are services to which you submit jobs to perform.