> OS threads are expensive due to statically allocated stack, and we don't want that. We want cheap threads, that can be run in millions on a single CPU. But wi

> OS threads are expensive due to statically allocated stack, and we don't want that. We want cheap threads, that can be run in millions on a single CPU. But without the clumsy "async/await" words. Green threads ("cheap threads") are still expensive if you end up spreading a lot of per-client state on the stack. That's because with async/await and CPS you end up compressing the per-client state into a per-client data structure, and you end up having very few function call activation frames on the stack, all of which unwind before blocking in the executor.