Callendar · Google Calendar integration

Context

Callendar is a WhatsApp-based scheduling service for independent professionals in Latin America. I was hired for one specific job: integrating it with Google Calendar.

The problem

Clients booked over WhatsApp, but the professional's calendar lived in Google Calendar, and someone had to copy every appointment by hand. And the problem was not only technical: accessing a user's calendar requires permissions Google classifies as sensitive, and it does not grant them without a formal review. Without passing it, the integration cannot leave testing.

What I did

• Integration with the Google Calendar API through OAuth 2.0
• Preparing and passing Google's verification process for sensitive scopes: proving legitimate data use, publishing a privacy policy and terms, and passing a review with a demo video of the full flow
• Production deployment with Docker Compose and process management

Outcome

Integration verified by Google and in production. The service is still running.

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