Lemm.ee has horizontal scaling, and afaik it’s the only lemmy instance to have added it. He has a sticky on meta@lemm.ee that talks about how he’s using a half dozen different servers to split the load, although there’s a few services that can’t be split like image caching, so they just get their own server. I think the changes are being pulled into future updates so hopefully other lemmy instances can start doing the same
It’s a really cool technology, but the main problem is that letting people around the world inspect and verify just isn’t needed in most use cases. It does a great job at removing the central source of truth, but rarely does anyone explain what the problem with a central source of truth was. Especially when you’re talking about a company setting, startups don’t want to build open source software without a source of truth, they want to be the source of truth