For better or for worse, this fragmentation on the fediverse (which causes the missing replies and posts in smaller instances) is what allows fediverse instances to be hosted by smaller actors and one of the most important reasons I feel the fediverse can and will survive (regardless of how popular other services become)

It feels quite unrealistic that a hobbyist or even small organisations would ever be able to fully host bluesky. Unless I’m fundamentally misunderstanding something about how it works.

Can relays be lazy, be used by a limited amount of users and just stream those users activities plus what they follow? If that is possible then I guess you’d be losing the benefit of algorithmic feeds, though… or again I fundamentally don’t understand something about the protocol.

If it’s related to managing state I think you might be looking for Custom Stores.