Sodium/Embeddium Addon: Substrate
This mod is a fork of the Bedrodium project created by developer kirillirik.
Mandatory requirement: The Sodium mod must be installed for it to work.
Substrate offers a small but effective performance optimization by removing invisible sides of the bottom and top layers of the world. These edges are displayed to the player only when it's actually necessary. For example, in the Overworld, polygons of the bottom layer will be removed, while in the Nether—both bottom and top layers.
Interestingly, despite the bedrock-related theme, the mod doesn't check block types and provides benefits even on floating island maps, which are common on mini-game servers!