Pre-Billing Notification System

A distributed, event-driven notification system that schedules and delivers notifications to users before subscription billing events.

Features

• REST API for scheduling and managing notifications
• Redis-based message queue for reliable job persistence
• Horizontally scalable worker services
• Multi-channel delivery (email, webhook, SMS)
• Automatic retry with exponential backoff
• Comprehensive monitoring and health checks

Tech Stack

• Runtime: Node.js with TypeScript
• API Framework: Express
• Message Queue: Redis (using ioredis)
• Testing: Jest with fast-check for property-based testing

Project Structure

src/
├── api/         # REST API endpoints
├── worker/      # Background worker service
├── queue/       # Redis queue operations
├── channels/    # Notification delivery channels
├── models/      # Data models and types
└── utils/       # Utility functions

Getting Started

Prerequisites

• Node.js 18+
• Redis 6+

Installation

npm install

Development

# Build the project
npm run build

# Run tests
npm test

# Run tests in watch mode
npm run test:watch

# Start API server (development)
npm run dev:api

# Start worker service (development)
npm run dev:worker

Configuration

Configuration is managed through environment variables. See .env.example for available options.

Testing

The project uses a dual testing approach:

• Unit Tests: Verify specific examples and edge cases
• Property-Based Tests: Verify universal properties across randomized inputs using fast-check

Run tests with:

npm test

License

MIT