> Performance is similar to when I self-host Forgejo on a dedicated VPS where I'm the only user, which is super fast.

I don't mean to be negative, but that's probably because it's pretty much the same thing. Codefloe is tiny. Some quick counting shows it has a grand total of 1012 registered users, including bots, and 1416 public repositories of which the top 3 with the most stars (I know this is a mostly meaningless metric, but for scale) have 27, 13, and 8. It's too small to run into scaling issues.

That’s an interesting question - it’s one thing to run an instance of forgejo for a limited user base and another to run at mass public scale.

How does someplace like a GitHub/Gitlab go it? Are user accounts or repos sharded across different servers? Is there a different underlying scaling system? If one wanted to run Forgejo “at scale” what would it really require, or does this need to be factored into the design from day one?