Agreed. Exp Full stack Web dev here. This slowness is clearly a dev issue. The “it keeps spinning” is rarely a db issue or server issue IF the server has power and this one has. This smells to much like something is timing out . I also noticed that when I reply to someone who was logged in from kbin (or even mastodon) it just never ever submits.
I’m not that familiar with federation itself. But I do know my way around the web. I too hope that they fix this asap. It could even be something like a non sorted query. Or just an endless/to long loop. These are the most typical bugs that happen when there is more data.
Anyway just my 2 cents. Like I said I’m not that familiar with the Lemmy code.