SpigotMC

SpigotMC, also known simply as Spigot, is a fork of the popular Bukkit server mod. Spigot is meant to increase performance and efficiency, while maintaining compatibility with Bukkit plugins.

Usage on servers
Many larger servers use Spigot, since they tend to use more resources than an average server. Spigot is also ideal for home servers that cannot buy hardware upgrades or pay for server hosting. Home servers tend to lag a lot, typically due to network lag, and the fact your computer has to process the game, the server, and your operating system.

Features

 * TPS increases
 * Optimized growth, decay and chunk ticking
 * Auto stack merging for items and experience orbs
 * Chunk garbage collector to prevent chunk leaks
 * Configurable values for many vanilla/Bukkit messages (e.g. whitelist, no permission)
 * Disabling of random light updates
 * Efficient Netty networking engine
 * Smart crash and hang detection / prevention
 * Entity activation and tracking ranges to ensure client-side and server-side resources are only used when needed
 * Prevent server load caused by maps in item frames
 * Ability to disable TAB command complete
 * Customization over what the console logs (minimal)
 * Fine control over growth rates, chunks, and ticks
 * Optimized tick loop
 * Memory-reducing nibble arrays
 * More accurate benchmark timings reports
 * Configurable chunk packet sending
 * Threaded chunk compression

Other Optimizations & Alternatives
An optimized version of SpigotMC is PaperSpigot, which has more optimizations and is ideal for servers such as anarchy servers which consume a lot of resources.