I’m discovering reactive programming with Spring WebFlux and Netty. When we call some external service we make a request with WebClient, receive a publisher(Mono or Flux) and at the same moment release thread for doing some useful work with other client requests. So question tormenting me is: Is there any thread listening for a response from an external resource? How do we get a response if we don’t block calling thread, who (which thread) controls response receiving and returning it to client?