What is Pict-rs?

The image-hosting component: https://crates.io/crates/pict-rs

I wonder if you could replace Postgres with CockroachDB in this instance to scale out.

It's not a crazy idea, but it's not obviously a panacea either.

• Cockroach is harder to admin and would only provide benefit on giant instances. It would be worse for small/beginner instances, which is the majority of them right now.
• Cockroach doesn't support the full PG protocol, there may be porting issues.
• Cockroach can have poor performance on some query types. I don't have deep knowledge of what kinds or if Lemmy would be impacted, but when I read about cockroach migrations it's common to find some performance footgun people had to work around. This can also add to the porting effort and could make it harder to develop for Lemmy on cockroach.
• There's also AWS Aurora, for distributed PG-compatible dbs.
• Finally Postgres scales pretty big. You can't run reddit or Facebook on a single-write leader with a bunch of read replicas, but you can run a pretty big website that way.

All of which is to say, maybe there's something there... but often distributed databases have fewer features and have bigger footguns than rdbms's. If you want to try cockroach or aurora, you don't need the devs help. You can stay to stand up a Lemmy instance that points at them. If the compatibility is really good enough, it will "just work" and you can try some performance testing. If it doesn't, then you have your answer than porting effort is requires for speculative benefit.