The gfpakhashcache.bin file is a harmless "map" used by your software to find and verify data quickly. It’s the difference between a game starting in 10 seconds versus 60 seconds. Unless it is taking up an unusual amount of space (which is rare, as these files are usually small), it is best to leave it alone and let it do its job.
Instead of just Path -> Hash , the new .bin structure includes a small metadata block per entry: gfpakhashcache.bin
If you're experiencing issues with this file, such as errors when trying to access or delete it, or if you're curious about its purpose, here are some general points that might help: The gfpakhashcache