The kernel is ultimately the thing that preempts your process and allows it to be killed, restarted, etc. It's also what handles things like "the connection was

The kernel is ultimately the thing that preempts your process and allows it to be killed, restarted, etc. It's also what handles things like "the connection was dropped", or "the thing timed out", etc. Userland facilitates management of those actions in a user oriented way through helpers like systemd or your container orchestrator or whatever. It doesn't make much difference though, you can say it's systemd, the kernel, dockerd, or whatever. The point is that operating systems have tons of facilities built in for the management of processes. > Sorry if I was unclear, I meant it as "I don't want to worry if the kernel will properly schedule N clones of my single-threaded program so I prefer to write a fully async one in a single OS process and work on it to make it efficient instead; failing that, I'll just bump my hosting so my program has the throughput I require". Why not "I don't want to worry about if my kernel will properly schedule N clones of my single threaded program so I'll just bump my hosting so my program has the throughput I require" ? Also I didn't suggest single threading, I generally build things as 'async/await' on the inside and 'service oriented' on the outside. So when there's some new domain I don't spawn a new task, I just spawn a separate process.