title: How to push the result of an asynchronous REST call to the client using REST and Kafka
body: <p>I want to deploy a scalable set of microservices. Every service should communicate via REST to each other. Also I need to request third-party services which will be slow and unstable. 
  So I came up with the idea to make it event-driven and use apache kafka.</p>
  
  <p>Something like:</p>
  
  <p>WebClient_X--request--->LoadBalancer--forward-->A-Service_1--request--->ThirdPartyService</p>
  
  <p>A_Service_1 needs to poll the ThirdPartyService for the results and writes them into kafka.</p>
  
  <p>A_Service_1--->Kafka</p>
  
  <p>Now what?</p>
  
  <p>How is it possible to send the results stored in the kafka topic back to the requesting WebClient_X. 
  Remember:
  - A-Service is deployed N-times behind the LB.
  - the A-Service_1 instance returned a Response.created(uuid) to the WebClient</p>
  
  <p>On solution would be to make the WebClient consume the kafka topic. But this seems to be a stupid idea.</p>