title: Kafka Stream: output to a topic first or persist directly?
body: <p>A fair number of articles describe implementing the use of Kafka Streams where they output to a new Kafka topic instead of saving to some sort of distributed database.</p>
  
  <p>Is this just a common use case, making the assumption that the embedded db + interactive queries is sufficient, or is there some architectural reason why one would want to output a topic before consuming it again to persist it, instead of persisting directly? </p>
  
  <p>I'm not sure if it makes a difference, but the context of the examples I'm looking at is for tumbling time-windowed aggregation.</p>