And if it's for something with high traffic, why would you want a cloud function anyway? I thought they are meant for "runs sporadically, so why have a machine that's always on?" setup.
Is this possible without AWS? Certainly. I was one of the two people who wrote the queue subsystem for Drupal more than a decade ago. And yet, AWS here does away with all the scalability concerns both up and down.
The landscape is changing too. So if your work is stateless or relatively low bandwidth, and has variable load then it's probably worth trying FAAS.
I used to do that for side projects, but I've had too many servers, and maintaining them was a pain.
For something with high traffic, Lambda provides the instant scalability. Imagine servers autoscaling, but instantly. And again, without having to setup or maintain that.
You're confusing a root server or a VPS with a webhost aka "shared hosting", where the hosting service takes care of Let's Encrypt certificates, and scheduled downtime for patching.