Looking at the Linked Instances, most instances have at most a few hundred instances linked. What happens when there are thousands, or possibly even millions? Could too many instances require significantly more powerful hardware, or even be impossible altogether?
I think there’s a lot of nuance here. I mean the Fediverse isn’t super efficient. But it manages to do what it’s supposed to do. And it really depends. Which Fediverse software. How many people are on those servers, how are they distributed. Do groups of people mingle on certain servers. Do they all subscribe to all the same content out there. Are there really big groups on servers with happen to have a slow internet connection… And then of course can we come up with improvements if we need to.
I think we’re going to find out once (or if) the Fediverse grows substantially. Some design decisions of the Fediverse are indeed a bit of a challenge for unlimited growth. Oftentimes technical challenges can be overcome, though. With clever solutions. Or things turn ot differently than we anticipated. So I don’t think there’s a good practical and straightforward answer to the question.