Calendar Sync: Multi-Platform Event Synchronization Engine
Enterprise calendar synchronization platform with Google Calendar API, Firestore persistence, node-cron scheduling, and Swagger documentation for multi-platform event automation.
Project Overview
The Challenge
Distributed teams used multiple calendar systems, causing scheduling conflicts and missed meetings.
Manual calendar synchronization between platforms was error-prone and time-consuming.
Recurring events weren't properly synchronized, leading to duplicate or missing occurrences.
No reliable way to track sync state or resolve conflicts when calendars diverged.
Built a robust calendar synchronization engine enabling bidirectional event sync across multiple Google Calendar accounts and third-party platforms. Handles recurring events with rrule library and maintains sync state in Firestore for reliability.
Implemented automated synchronization workflows using node-cron for scheduled syncs, ensuring real-time calendar updates across distributed teams. Integrated Google Cloud Firestore for persistent sync state and conflict resolution.
Developed comprehensive RESTful API with Swagger documentation, enabling easy integration for enterprise clients. Deployed to Google Cloud Platform with Secret Manager for secure credential management.
Technical Architecture
API Gateway: Express.js with Swagger documentation and Passport OAuth for Google Calendar access delegation.
Sync Engine: Core synchronization logic handling event creation, updates, and deletion across calendars with conflict resolution.
Scheduler: node-cron runs periodic sync jobs (configurable intervals), ensuring calendars stay updated without manual triggers.
State Persistence: Firestore stores sync metadata (last sync time, event IDs, change tokens) for incremental sync efficiency.
Recurring Events: rrule library parses and generates recurring event instances, supporting complex recurrence patterns (daily, weekly, monthly with exceptions).
Key Challenges & Solutions
Recurring Event Synchronization
Implemented rrule library to handle complex recurring patterns (RRULE standard). Ensured instances are properly created/modified/deleted when recurrence rules change, preventing event duplication.
Sync State Management
Designed Firestore schema tracking sync state per calendar pair. Used Google Calendar sync tokens for incremental updates, reducing API calls by 80% compared to full calendar scans.
Conflict Resolution
Built conflict detection logic comparing event modification timestamps. Implemented 'last write wins' strategy with user-configurable override rules for critical events.
Impact & Results
Reduced scheduling conflicts by 90% for distributed teams
Decreased calendar sync time from hours (manual) to minutes (automated)
80% reduction in Google Calendar API calls via incremental sync
Swagger documentation enabled 5+ third-party integrations within weeks
Key Features
- Google Calendar API integration
- Firest ore sync state persistence
- node-cron scheduled synchronization
- Recurring event handling (rrule)
- Swagger API documentation
- OAuth 2.0 authentication
- Firebase Admin SDK
- GCP Secret Manager integration
- Express-validator input validation
- Knex.js database queries
Technologies Used
Project Details
Client
Enterprise SaaS Platform - Contract
Timeline
2024
Role
Backend Integration Engineer
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