Its now running on a dedicated server with 6 cores/12 threads and 32 gb ram. I hope this will be enough for the near future. Nevertheless, new users should still prefer to signup on other instances.
And it's not even a super beefy one!
kbin.social uses a CCX41 with 16 virtual cores (I think 8 of those are hyperthreaded though) and 64gb of ram for its ~25k users