LazyDFU Mod (1.19.2, 1.18.12) is an optimization mod which makes initialization of DataFixerUpper lazy. This means that it won’t immediately create the rules necessary to migrate data from older Minecraft versions to the newer ones until it is actually needed. While it does not alter DFU, you should use more caution than usual.
LazyDFU’s premise is that you won’t need to convert data for all versions of the game. DFU rule compilation happens later, after the game is up and running. It is possible to experience lag spikes when LazyDFU forces you to compile migration rules. However, once the game is complete, there is no performance penalty.