Does CubeBackup work through official Google APIs or through some other method?
Google APIs only
All communication with Google's servers is done through official Google APIs, including Google Drive API, Gmail API, Google Workspace Admin SDK, Google Calendar API and Google People API.
CubeBackup uses OAuth authentication over HTTPS both to fetch Google Workspace data and store it locally, and to restore it to the cloud again. More information is available from Google Developers.
Network communication
All communication is strictly between your backup server and the Google cloud using HTTPS protocol. No data is routed through our servers or any third party.
Local SQLite files are used to track folder and file revision histories, so that only changes to your files are downloaded, much like GIT.