Terraria: world size, players, and what actually causes lag

A Terraria server spends most of its memory on the world rather than on the players in it. That is the single most useful thing to know when deciding how far a pass will carry you: a large world with four people is heavier than a small world with eight.

Pick the world size before the player count

World size is fixed at generation and cannot be changed afterwards without starting again. Player count can be raised whenever you like. So the order to decide them in is world first, players second — the reverse leaves you regenerating a world you had already built in.

What actually causes lag

• Large numbers of items dropped on the ground, which are never cleaned up on their own.
• Very long wire and conveyor contraptions, which are evaluated every tick whether anyone is near them.
• Town NPCs housed far apart, which keeps distant parts of the world loaded.

None of these is fixed by more memory. If your world has slowed down over months of play, it is usually one of the three above rather than the pass it is running on.

Freezing between sessions

If you are not going to play for a while, freeze the world. The save goes to cold storage, the compute is released, and thawing puts it back — on any idle pass, not necessarily the one it came from. Nothing about the world changes in the meantime.