Where does the Windows 10 Photos app store its catalog files?

Where does the Microsoft Photos app store its metadata, such as album contents? I'd like to synchronize these files between two machines so both can access the "same" photo library. (The photos are already stored in a common network-accessible location and I'm aware of the potential for destructive race conditions.) I poked around AppData, where such things usually get stuffed, but couldn't find anything.

This is the Photos app that's installed by default on Windows 10, from the Windows App Store. I'm running version 2017.35063.13610.0 in case that matters.

I found it -- the files are in AppData\Local\Packages\Microsoft.Windows.Photos_8wekyb3d8bbwe\LocalState, and the catalog appears to be held in an SQLite database therein. Unfortunately, syncing the files didn't work out since it seems that Microsoft Photos keeps running in the background even if it's been "closed", so the files are always locked and cannot be replaced. Even if they could, Photos canonicalizes file paths so if the photo library is on one of the machines then it'll force the local path instead of using the universal network path, and the database won't work on other machines.