Apache Flink is also a good alternative, and works very well. We have used it in production for a while for generating live reports. I made simple example [1] and have a look at the docs if you are more interested [2]. Gonna definetely try Kafka's version, its version of stream processing [3] also interesting as well.
[1] https://medium.com/@mustafaakin/flink-streaming-sql-example-...
[2] https://ci.apache.org/projects/flink/flink-docs-release-1.3/...
[3] http://docs.confluent.io/current/streams/index.html