Webserver to Kafka communiction

I am not a java expert. I was curious as to how the webserver talks to Kafka via the consumer ? It seems like the consumer is running on a separate thread ? What was the rationale behind the decision ? Also does it mean there is one consumer per request into the webserver ? Does the solution scale to many many consumers ?

EDIT: reposted as an FAQ wiki, but please feel free to answer here.
