Lemmy uses PostgreSQL, with a number of tables. It’s pretty standard stuff, looks like, and it’s in Rust. It’s assumed there’s only going to be one server per instance right now, but I’d expect that one server could keep up with a reasonable volume.
I already get rate-limited like crazy on lemmy and there are only like 60,000 users on my instance.
Is that a typical number of users to have already? Wow, we really are growing.
Rate limiting is it’s own thing, I guess some work will need to be done to find a non-exploitable way to do it that still scales.