Internal Server lags horribly.

The game lag is getting better with this snapshot however the internal server that runs single player is lagging horribly. It takes about 30 seconds to render new chunks so by the time you get to them you are walking in air until the chunks finally render. Also, when I first started a game on the new snapshot; the first thing I did was break a piece of wood from the tree and then the wood reappeared on the tree. This is sure sign of the server lagging and this also takes about 30 seconds before the wood finally disappears and goes into your inventory. My computer is too slow to run the game and a screen recorder at once so I can't prove my point. According to the Wiki it says that the game is being tailored toward old and slow computers. Well I have the disagree the game is faster but the internal server that processes the chunks and player actions is severely toast. This HAS to be addressed before 1.9 is released or else I won't be playing it.