@grishka but you're not leaving. You're just doing a request to the followers collection and interpret it in your backend/frontend.
That's what I meant by "another data store". Instead of querying your own db, you have a wrapper over the C2S activitypub API. :D
@mariusor oh okay, I get it now. But I need more complex stuff that requires having a complete list at once, like common friends. Even just showing a friend list for a Mastodon user wouldn't work here — you need to intersect their following and followers lists.