@darius some super back of the envelope math from some numbers i have from working at twitter a while ago suggests if you converted all twitter's compute resources into fedi servers it could pretty easily support the same number of MAU that twitter had on fedi. that doesn't take into account things like inefficiency in individuals running servers (although the fact that most people run them on VPSes probably makes that moot) or network bandwidth (not sure how RPC fanout compares to activitypub traffic, this probably depends on the degree of centralization we end up with), but the order of magnitude seems about right.

twitter ran in a highly inefficient way, not to mention massive amounts of compute spent on ML models for ads serving, timeline algorithm assembly, etc, so it's pretty easy to do better than that :p