minestom/minestom ? reverse-engineered prompt

Build me a lightweight Minecraft server library in Java that I can use to make my own custom server from scratch.

I want the server to be focused on performance and not include vanilla game features by default, but it should still give me a solid API for the things I need most, like players, entities, blocks, inventories, commands, and custom world like instances. It should be easy to create different areas of the game on the fly, move them around, and handle them efficiently without the usual server overhead.

Please include a small demo project I can run to see how it works, plus clear docs or examples for getting started. Keep it modern and developer friendly, and make sure it feels like something built for minigames or creative style servers rather than a vanilla survival server. If you need to, look up current docs online for Minecraft protocol or API details.