I mean consider e.g. some code in a standard Rails monolith raises an Exception. The exception bubbles up and is caught by a middleware that displays a status 500 page. Isn't that basically failure recovery too? Or for the same Rails monolith, one worker process hits bad code that eats memory until it is killed by an OOM-killer. Unicorn/puma notices that the worker process is missing and restarts it. Is that more analogous? In either case the request is failed but the server pretty much "recovers", ready to accept new requests.

So what is unique about the supervised processes with built-in failure recovery approach? Or am I viewing this at the wrong level of resolution or something?