[sethammons]

Kafka shines when you have multiple services that have data to publish and multiple services that need to read that data stream. If you have three services and they write to ES, publish metrics to some other store, and log events to the db, you could instead write that all to Kafka, and individual consumers can use the data (for instance, to put into ES). On the origin-service side, it has one integration point; it does not need to know about ES. Now let's say that your users want a near real-time dashboard of their data changes on your multiple services. All you do is make a new consumer from Kafka. You don't add it to your three services. Kafka simplifies your service relation graph.

[balamaci]

Well I definitely support the example of using Kafka for analytics with a streaming solution like Flink or Spark, etc. However I asked the "why not directly to ES" question because the example of using Kafka just as a layer in front of ES I felt it kinda painted Kafka layer as something "we could do because we can, not because we need to".