Async Await Is Just a Bookmark

https://www.youtube.com/watch?v=2ulRI-a5ea0 Here's what most developers think async/await does: you call an async function, and it runs on a separate thread. Maybe a background worker. Something parallel. Wrong. Async/await does not create threads. It does not run things in parallel. One thread. One function at a time. Always. So how does your app handle a thousand network requests on a single thread? The Compiler Rewrites Your Function When you write an async function, the compiler doesn't keep it as a function. It transforms it into a state machine . Each await keyword becomes a checkpoint. State 0 runs the code before the first await. State 1 runs the code between the first and second await. State 2 picks up after that. The function remembers which state it's in and all its local variables. When execution hits an await , the function doesn't block. It doesn't spin. It saves its state and returns control to the caller. The function literally pauses itself. The Bookmark Metaphor Think