I've been having this problem for a few days now where myself and my friends all can't log into my realm, the game gets stuck on the load in screen, and on the rare occasion that we do get logged in we experience major lag, blocks look like they break but nothing drops, the game is virtually unplayable and we often get disconnected.
At first I thought the issue may have been over building/spawning too many things in one chunk but we have since rolled back the realm to a previous save where it was still playable and then spread out our builds but we are still having the same issue.