Worldthreader

Worldthreader moves the work of each dimension onto a separate thread, so the server can process several dimensions at once. The mod is built to keep vanilla behavior in most cases, and it changes how entities that go through portals are ticked, delaying the tick that follows their departure. A gamerule named worldthreader AdditionalEntityTickAfterTeleport can make entities teleporting into the overworld tick once more after they are placed in the world.

Worldthreader also changes the order of commands that touch the shared scoreboard across dimensions. Commands within a single dimension keep their vanilla order, but interdimensional commands from command blocks can be observed in a different order, since interdimensional ordering is not promised within one game tick. Worldthreader always keeps all dimensions in step, so the overall tick time follows the slowest individual dimension.

The server needs Fabric API to use the gamerules, and without it the mod falls back to default settings. Only the server is needed for multiplayer. Singleplayer worlds also need the mod on the client, so the environment is server-side only for servers. Compatibility issues with other mods are common; the author asks that problems be reported to the mod directly.