Where does Web Crossing keep its data?

Web Crossing keeps all it's data and control panel settings in the file called webx.db

With Version 3.1, certain control panel settings are also written to a file called webx.set, which can be modified with a text editor. Values in webx.set will supercede settings in the database at boot time. However, any subsequent changes to control panel settings will cause webx.set to be re-written.

Web Crossing uses a proprietary read-optimized database, that's why it's so much faster than other systems that use backend database engines that are write-optimized.