I have a map size of 559.2MB and before the update (0.13.0) I used to play okay in it.
After the update, game start fast and nicely flowing but after a short while it starts to get really slow and laggy and it comes to I could not even turn the head of the Steve Dude! Front, back, right, left and on creative up and down fly works just fine but all gets loaded very slow and laggy as time passes within the game.
When I get out of the game for even geting out of the game it makes me to wait for the buttons to catch the clicks. When I get out safe and sound (No Crash) and when I get back into the game all starts well and as I roam in the map/game it starts to get slow and laggy again.
This happens only when monster grinders provide tons of monsters that game gets laggy and slow and now on regular play after the update 0.13.0
All related issues to lag are pretty much about the same thing.