Okay, I have a server running the database (postgres) that backs my user-facing apps. How exactly shall I run kernel/glibc/systemd/postgres updates without customer-facing outages?
EDIT: To be clear, I'm mostly arguing that you're wrong, but if you have a solution then that'd be great, because I dislike the difficulty in patching these things.
I remember building a system about 15 years ago which automatically failed over in under a second - the application connected to the most recent one and set up replication to the other one. If the master went down then the slave was promoted to master and when the original master came back it was configured as slave.
I certainly don’t have auto updates on all my servers (wouldn’t be good if a tv program going out to millions of people suddenly vanished — there’s always a glitch when it fails over), I do have it on public facing servers though, so in your case I’d have it on the web servers but not on the database.
EDIT: To be clear, I'm mostly arguing that you're wrong, but if you have a solution then that'd be great, because I dislike the difficulty in patching these things.