What I mean is: async/await is just syntactic sugar over promises/futures and those just buy you a way to schedule future computation. The js runtimes schedule

What I mean is: async/await is just syntactic sugar over promises/futures and those just buy you a way to schedule future computation. The js runtimes schedule all your code on a single thread. It's the fact your code only runs on a single thread that 'solves concurrency' because data races can't happen if one thread of code is allowed to access memory at a time. You can set up the same limitation in a threaded program/language, and people have (see vert.x, clojure STM, and others).