Optimization mods are easiest to evaluate when safety and measurement are part of the same process. LazyDFU is narrow in scope, but the surrounding actions—changing loaders, game versions and world data—still deserve backups and controlled testing.
Back up before changing version-sensitive components
Keep a copy of important worlds outside the active instance before upgrades. A backup is especially valuable when a world may trigger data migration rules after opening in a newer game version.
Verify provenance and file type
Know whether you have the original Fabric project, an unofficial port, a compiled JAR or a source archive. Similar names do not guarantee identical code, loaders or supported versions.
Benchmark startup correctly
Measure from the same launcher state, run several launches, and compare medians instead of one best result. Keep the mod list and Java settings unchanged during the comparison.
Expect a possible deferred pause
The original project explains that if migration rules are later required, rule compilation can cause a lag spike. That is the expected cost of deferring work rather than doing it during every startup.
Related next step
Use the compatibility information above before choosing a download. If you only have the supplied master.zip, remember that it is source code rather than a normal mods-folder JAR.