Google Calendar two-way sync

Booklink uses Google Calendar's push notification API to keep bookings and personal events in sync in real time. Once a user connects their Google account through OAuth, Booklink writes every confirmed booking as a calendar event on their primary Google Calendar, including the client's name, the service, and the booked duration. In the opposite direction, Booklink subscribes to changes on that calendar, so when the user adds a personal event (a school run, a doctor's visit, a holiday), that time slot is marked as busy on their public Booklink booking page. Clients cannot book over those times. Each team member on a Pro plan connects their own Google Calendar, so personal events only block that individual's availability, not the whole team's. Booklink only reads free/busy information from events it did not create - event titles, descriptions, and attendees of personal events are never stored or displayed.