> And for good enough software you should consider that maximum already for any number of users.
I don't believe such software exists. (And, to be clear, I'm writing from direct, day-job experience.)
EDIT: I take it back. SQLite, cURL. Maybe.
EDIT2: I can't reply to the SEL4 response, so here goes. I'm a huge fan of verification tools, but consider the Spectre class of bugs. Verification is always done wrt a mathematical model that you've defined after inspecting the world and writing down the properties you want to track. But the world changes, and the chance that the world changes increases with the number of users of your software. That's the nature of the beast.
