Our story begins with a humble ‘await fetch’: your script fires off an HTTP request and settles down to nap, trusting that it’ll be awoken when response data is available. While your program does nothing, a cascade of activity is now taking place: in your JS runtime, your operating system, and your hardware. What happens while your code is waiting for something to happen? In this talk, we’ll peek behind the layers of the event loop, select/epoll nonblocking I/O, and …