It's very much possible.
If you use calibre-server though, I don't know if it needs to be shut down before you can copy the updated library from Mac Mini to RPi.
With something like COPS on the RPi, you don't even have to restart the server to push changes. I believe that one just opens and closes the database file (metadata.db) every time you load a page.
https://www.mobileread.com/forums/sh...d.php?t=170903