To support decentralization and spread, should lemmy.world close registration at some point to prevent a performance overload due to too many users? Of course, if registration is disabled, there could be a hint placed somewhere near that from other instances you can interact with content on lemmy.world just like you had registered on it. There could be a link to join-lemmys instance overview.
I honestly think during the sign up the registration to a server needs to be randomized to spread the load. That and allow the user counts to be global and not just to your instance and you then have user load balancing.
If we could also migrate our data between servers with a backup server option. When lemmy.world goes down, just switch to a different randomized backup server.
The danger in randomizing servers is that some smaller servers not only have less than 99% uptime but are also just run by random regular people who couldn’t handle the increased load and/or have no desire or ability to keep the servers running long term. It could maybe work if the randomization occurs from within a vetted list.
Account migration is a feature that has been noted for the future and would indeed be very important since it would essentially make the entire network bulletproof. Being able to move instances and/or link accounts across multiple instances would create the necessary redundancy and reduce fears of choosing a smaller instance as home.