Backend & systems·Concurrency and coordination
the thread issues the request and goes off to do other work instead of sitting there waiting for the socket.
Non-blocking I/O
Also calledasync I/O, asynchronous I/O
I/O that returns immediately and notifies you on completion, so one thread can have thousands of operations in flight. It is what lets a small number of threads serve very high concurrency for I/O-bound workloads. It buys nothing for CPU-bound work, and one accidental blocking call inside an event loop stalls every request on that loop.