Core Database Rebuild - Affects on back up drive?

On completion of rebuilding the Cores database via the app. Followed by a “back up” to an external hard drive sometime in the future.

Is this new “re-indexing file” (?) post database rebuild, placed on the back up drive, as an additional file OR does it over write the original. I assume it is only this indexing file(?) that would be be affected ie. not a complete back up from scratch, taking days?
If this was a complete back up from scratch, does it overwrite the original back up files on the back up drive or do you load up unnecessarily the back up drive with large files?
In this case, it would seem sensible to delete the old “image” from the hard drive using a windows lap top, assuming it can be easily detected.

I have no knowledge regarding the size of this indexing(?) file, but seems unnecessary having either a previous corrupted index file on the back up (eg. due to loss of images, in my case, only the down loads), OR for that matter having additional files taking up space on the back up drive.
IF these data base rebuild files do get stored (on back up), again is it worth deleting the “old file” if you can detect it, when connected to a windows laptop?

Rebuilding the database index over-writes the old index file and if you backup, it doesn’t mean backing up all the music again. The index file is small (like the index in a book is small!?!).

Don’t over-think this. It’s not a problem to worry about. Best not to go deleting things because you don’t need to and you might break something.

Thanks for explanation - now clear.