Apache was a bad analogy. There is a thing that needs to be multi-process and fault-tolerant with the default case of badly-written code tossing out more state than just your own session, but it's not a web server that works like that.

Instead, it's a "web application server", like Puma is for Rails apps: a server that runs your code in its own address space, where your code can crash the active worker process (which is usually handling multiple requests) for that server.

Puma ordinarily runs ~eight worker processes, and a crash will kill one of them causing it to take the time to re-fork, and discard any other sessions that were also scheduled on that worker. Erlang runs a million worker processes, and one of them crashing doesn't cause anything big to happen at all.