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Kalender-Sync

Kalender-Sync

SaaS tool for synchronizing calendars across platforms — Google, Microsoft, Apple (CalDAV), and iCal feeds. 26 beta users, 16,000+ synced events.

TypeScriptNode.jsPostgreSQLCalDAVOAuthSaaS
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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. Currently in closed beta with 26 users and over 16,000 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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