In our C++ stack at work we accept HTTP requests, and then spawn internal IO which takes some time. During that time, we yield the handler thread to handle oth

In our C++ stack at work we accept HTTP requests, and then spawn internal IO which takes some time. During that time, we yield the handler thread to handle other requests. The arrival of the internal response sets up the next step in the request handler to resume, which needs the response message. This can be done manually by polling status of descriptors, and stepping into and out of callables / passed continuations by hand, or it can be done with a task scheduling API and typesafe chained async functions. Pick your poison, I guess, but it probably scales better than using synchronous IO and thread-per-request.