The thought of having my calibre library stored anywhere other than a local drive is downright scary. There have been too many posts through the years where people have written "I had my calibre library stored in cloud provider/on a NAS/etc. and now I've lost my books/metadata doesn't work/my library is corrupted/etc."
Basically, SQLite is not intended for use in a networked environment and eventually, it bites you in the butt. You might want to read through
SQLite Over a Network,
Caveats and Considerations for a more detailed explanation.
Yes, I do store backup copies of my calibre library in the cloud as well as on backup media and a local NAS. I would never try to use those copies as my live data.