title: Kafka: How to retrieve a response from consumer?
body: <p>I wish to describe the following scenario: 
  I have a node.js backend application (It uses a single thread event loop).
  This is the general architecture of the system:
  Producer -> Kafka -> Consumer -> Database</p>
  
  <p>Let's say that the producer sends a message to Kafka, and the purpose of this message is the make a certain query in database and retrieve the query result.
  However, as we all know Kafka is an asynchronous system. If the producer sends a message to Kafka, it gets a response that the message has been accepted by a Kafka broker. Kafka broker doesn't wait until the consumer polls the message and processes it.</p>
  
  <p>In this case, how can the producer get the query result operated on the database?</p>