KStream-KStream Join vs KStream-KTable Join Performance

Question

I have a Kafka Streams Application which takes data from few topics and joins the data and puts it in another topic.

Kafka Configuration:

5 kafka brokers
Kafka Topics - 15 partitions and 3 replication factor. 

Few millions of records are consumed/produced every hour.

I am making KStream-KStream join which creates 2 internal topics. While KStream-KTable join will create 1 internal topic + 1 table.

Which is better in terms of performance and other factors ?

Answer 1

The choice is not a question of performance, but a question of semantics: what should the join result be? Both joins, do compute quite different results so you should pick the semantics that meet your application needs.

The different semantics are documented in CP docs and AK wiki:

• https://docs.confluent.io/current/streams/developer-guide.html#joining
• https://cwiki.apache.org/confluence/display/KAFKA/Kafka+Streams+Join+Semantics