When I visit kbin.social, I see new posts regularly. On other servers posts stay on the frontpage for multiple days. This is also true if I switch their sorting to “hot”. So that is probably not the difference.
What is kbin.social doing differently?
Kbin uses a completely different backend and is nicely optimised. The owner (Ernest) is also investing in server space to accommodate the higher user activity.
They might answer you themselves, I’m sure they’re lurking here somewhere. 🙃