It's 8 K B per thread, so you can scale a thousand times further than you thought. One dark secret of the async movement is that if your goal is C10K (10,000 concurrent clients) then actually bog standard threading will handle that fine these days.
> The better async code and interfaces become, the more it looks like regular old multithreaded code, except there aren't actual threads underlying it. You still need to make sure you serialise access to shared resources, don't share data that shouldn't be shared, etc. All the same considerations as multithreaded code.
Depends what approach you're using. I prefer making an explicit distinction between sync and async functions ( https://glyph.twistedmatrix.com/2014/02/unyielding.html ), so you effectively invert the notion of a "critical section" - instead of marking which sections can't yield, you mark which sections can yield, so your code is safe by default and you can introduce concurrency explicitly as and when you need it for performance, rather than your code being fast-but-unsafe by default and you're expected to fix a bunch of rare nondeterministic bugs with minimal support from your tools, which is how it works in a multithreading world.