It seems the Mastodon ecosystem has serious problems scaling.
Most of the servers are closed to registrations, and we are just talking about a couple million new users over 2 months. What if 100 mil users want to move?
Are we going to relive the Twitter history, which crashed every time Justin Bieber tweeted?
I've tried telling people before that the Fediverse doesn't scale, that decentralized solutions where nobody is paying for anything only work for flashcrowds (i.e. torrents), and ultimately this is going nowhere... but nobody wants to hear it. Everyone is sure that "torrents work, so this will work", neverminding the fact that the entire peer-to-peer ecosystem only works as long as there are people to seed, seeding costs money, and there's plenty of content out there with zero seeders. You'd think that would clue people in that this isn't going to work, but there it is. Hell, you'd think the history of Usenet and FidoNet would've given people a clue, but nobody wants to hear that either.
If you're not willing to pay for the services you require... you're going to have a bad time. That is the ultimate lesson of the Fediverse.
Two observations: (1) maybe it doesn't need to scale for people to ultimately have a much better experience and (2) bottlenecks tend to be identified and resolved up to the limit of the scaling laws and hardware improvements, bandwidth cost reduction and storage cost reduction tend to over time make the impossible thing from yesterday feasible today.
Keep in mind that Torrents tend to be much larger than your average Tweet/Toot/Whatever and that the interconnects between the servers need to transport only those messages for which there are subscribers, something that could be optimized for (you really only need to transport each message once per sender if there are subscribers, not once per subscriber).
> maybe it doesn't need to scale for people to ultimately have a much better experience
It certainly needs less features. I'm sure quite a bit of Twitter's infrastructure is dedicated to ads and analytics.
That's a good observation, a federated, non-commercial messaging platform has a different tech footprint than one that needs to be monetized to the max to satisfy a bunch of shareholder and generate quarterly earning reports.