These are optimized server configuration files for CraftBukkit/Paper/Spigot/Purpur servers. These configs feature major performance improvements, with little to no changes to vanilla other than better performance improvements when compared to the default configurations.
Use the files at the top of this page and copy and paste them into your own! For example, if you run a PaperMC server, replace your paper.yml with the text from my paper.yml file attached above. Alternatively, you can delete and replace the entire file if you wish to do that instead. The same process applies for the other files.