Kalender-Sync
Live SaaS tool for synchronizing calendars across platforms — Google, Microsoft, Apple (CalDAV), and iCal feeds. 54 users, 38,000+ synced events.
The Problem
Anyone using multiple calendars for work and personal life — Google, Outlook, Apple — knows the struggle: events are scattered, scheduling conflicts go unnoticed, and manual sync is error-prone.
The Solution
Kalender-Sync is a SaaS tool that automatically synchronizes calendars from different providers. Users connect their accounts via OAuth or CalDAV and choose which calendars to mirror where. Publicly available since May 2026 on a freemium plan — Free, Basic (€4/mo), and Business (€10/mo). Current footprint: 54 users, over 38,000 synced events.
Technical Highlights
- Multi-Provider Architecture: Abstracted provider interface for Google Calendar, Microsoft Graph, Apple CalDAV, and iCal feeds
- Delta-Sync: Efficient incremental synchronization via change tokens instead of full sync
- Encryption: ChaCha20-Poly1305 for all stored OAuth tokens and CalDAV credentials
- Job Queue: pg-boss v10 for reliable background sync with retry logic
- Stack: TypeScript, Node.js, PostgreSQL, Drizzle ORM, Astro (Landing Page)
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