Just remember guys MediaPortal Trakt plugin supports two-way sync, so when they bring the API back online, any data corrupted and lost online will be put back by the MP sync (watched history, ratings).
No, those database files are just a local cache of what we get from the API. These are used for browsing around the plugin like providing watched icons and dashboards.
The databases I'm referring to are your plugin databases like mp-tvseries and movingpictures as these also store your history. When the trakt plugin does a sync it compares your local history with online, anything watched/rated locally and not remote, will sync across.
There is an exception to the cache files regarding your history, and that is with unwatched syncing. This is synthetic as the API endpoints I use do not support that, so I use the local cache files to do this (can't remember the details).