Here is a dashboard of synchronisation time between the most popular instances: …lem.rocks/…/federation-health-time-behind?orgId=…
As you can see, the only three instances synchronizing in more than 5 minutes are
- reddthat, based in Australia
- lemmy.nz, in New Zealand
- aussie.zone, Australia too
- feddit.ch, closing at the end of the month
For the 3 first instances, this is due to lag and centralization of communities on LW. Moving communities away from LW would actually help solving that issue (in parallel, Reddthat is planning to open an EU server to reduce the lag)
imaqtpie@sh.itjust.works 8 months ago
It usually is federated quickly within Lemmy itself. I can’t speak for kbin but in my experience on SJW, I typically get all the content from remote instances in real time.