title: How to filter messages before passing them on to consumers?
body: <p>I'm creating a lead and event management system with Kafka. The problem is we are getting many fake leads (advertisement). We also have many consumer in our system. Is there anyway to filter advertisement before going to consumers?
  My solution is to write everything into the first topic, then read it by a filter consumer, then write it back to the second topic or filter it.
  But I'm not sure if it's efficient or not. Any idea?</p>