You are side-stepping the question by explaining how scheduling works. You can not say that there is NO overhead. Using async code in a synchronous fashion is

You are side-stepping the question by explaining how scheduling works. You can not say that there is NO overhead. Using async code in a synchronous fashion is not going to be as fast as using plain sync code. Look at the wait() function: https://github.com/alexcrichton/futures-rs/blob/master/src/future/mod.rs#L270-L274 https://github.com/alexcrichton/futures-rs/blob/master/src/f... All this code IS overhead that wouldn't exist if the code was synchronous in the first place.