So, definitely a wave.
For the last eight hours Mastodon has been averaging over 3000 new users per hour, on track for 75K new users today. Overall, thanks to the amazing work of instance operators, the system seems to be running well, however there is definitely more lag than usual.
This new user rate, while high, is nowhere near what Mastodon experienced on Nov 18, when a quarter million users joined in one day. Still, this influx is very taxing on system administration.