I ask generally out of curiosity. I was just thinking that as big social media fractures, old school isolated forums might become “cool again”, and that one of the achievements of lemmy might be as a nice platform for simply running a forum for whatever community you want all without needing to worry about federation.
If it turns out that work of federating data is a substantial part of the resource overhead, and that an isolated server would actually be quite efficient, that’d be quite a nice feather in the lemmy cap I’d say. Hexbear seems to have been using lemmy this way for a while and it seems to have been successful too.
I have ~160 users and have been up about two months. We have subscribers to pretty much every large community and hundreds of smaller ones, plus media heavy ones like the NSFW communities.
Currently sitting at 6.6GB for Postgres (there was an update recently that drastically reduced the size, dunno exactly what it was at before), 54GB on pictrs/media. (I host the media on object storage, specifically Cloudflare R2)
For memory I’m pushing 3GB now, with Postgres taking about 1.5GB. That’s higher than it used to be, might be related to the update that reduced the DB size.
CPU: I have a cheap 2 core x86 virtual server/vps - and haven’t seen it go over 10% during normal operations…
To answer your question directly though, the most work is OUTGOING federation. So it really depends on how active your communities are/how many unique instances subscribe.