Everything, always, returns to a main event loop, even the actual hardware threads on your CPU. So JavaScript developers don't get a pass on this. The problem

Everything, always, returns to a main event loop, even the actual hardware threads on your CPU. So JavaScript developers don't get a pass on this. The problem is you keep creating async requests, they need to be stored somewhere, and that's in memory. Thread or no thread, it's in memory. And backpressure is essential, yes. Except for basic tasks. But there is another solution, which is coalescing requests. I.e. in my current project, I combine thousands of operations, each of which could've been its own async request, into a single "unit of work" which then results in a single async request, for all operations combined. If we treat IO seriously, we won't just fire off requests into the dark by the hundreds. We'd think about it, and batch things together. This can be done manually, but it's best done at a lower level, so you don't have to think about it at the business logic level.