EastEngine is a private Minecraft server implementation, most notable for its performance surpassing uSpigot in some environments.
In SMP configurations, performance patches are expected to break vanilla parity no more than Paper, though extra configuration can change this while still being more performant than Paper.
It also has additional security and configuration patches not found in other server implementations, which are particularly useful in offline-mode setups or old Minecraft versions.
Additionally, it contains a built-in, all-in-one, highly configurable anticheat that exceeds anything publically available, for any kind of server setup.
EastEngine is currently available for 1.8.9, 1.12.2, 1.21.11, and 26.2, with support for modded, hybrid (Bukkit x modded) and regionalized multithreaded (Folia) setups soon.
EastEngine is proudly ran on a handful of various servers, some private and some public, some being SMPs and some being minigame servers.
As of writing, EastEngine is only available to a small group of people and will likely remain that way for the foreseeable future.
Also see the CardinalDirector Minecraft L7 proxy