TODO.md

Eficientis Backend Challenge

This technical assessment requires the development of a robust URL shortening service using modern Node.js technologies. The service should provide RESTful endpoints for URL shortening and redirection while maintaining high performance and reliability.

Technical Requirements

The solution must be implemented using:

• Language & Framework:

  • TypeScript (latest stable version)
  • Express.js (latest stable version)

• Development Tools:

  • ESLint for code linting
  • Prettier for code formatting
  • Jest for unit and integration testing
  • npm as package manager

• Code Quality:

  • TypeScript strict mode enabled
  • Comprehensive type definitions
  • Code coverage reports
  • Automated formatting on commit

• Data Persistence (choose one):

  • In-memory storage
  • JSON file storage
  • SQLite database

• Optional Enhancements:

  • Docker containerization
  • PostgreSQL database with Docker Compose
  • Redis caching layer

API Endpoints

The URL shortening service should implement the following RESTful endpoints:

1. URL Shortening

• POST /api/v1/urls
  • Create a new shortened URL
  • Request body: { "originalUrl": "https://example.com" }
  • Response: { "shortUrl": "https://your-domain.com/s/abc123" }

2. URL Redirection

• GET /:shortCode
  • Redirect to original URL
  • Track redirection statistics

3. Statistics

• GET /api/v1/urls/:shortCode/stats
  • Get statistics for a specific shortened URL
  • Response includes: total clicks, unique clicks, timestamp of last click

Core Implementation Requirements

1. Core Functionality

   • Implement URL shortening algorithm
   • Handle URL validation
   • Implement redirection with proper HTTP status codes
   • Track URL statistics

2. Security

   • Implement rate limiting
   • Validate URLs before shortening
   • Implement proper CORS configuration
   • Handle errors gracefully

3. Testing

   • Unit tests for all business logic
   • Integration tests for API endpoints
   • Test coverage > 80%
   • Performance benchmarks

Data Model

classDiagram
    class ShortenedUrl {
        +string id
        +string originalUrl
        +string shortCode
        +number clickCount
        +number uniqueClicks
        +Date createdAt
        +Date lastAccessed
        -generateShortCode(): string
        -validateUrl(): boolean
        -incrementClickCount(): void
        -updateLastAccessed(): void
    }

    class ClickStatistics {
        +number totalClicks
        +number uniqueClicks
        +Date lastClick
        +Array<Date> clickHistory
        -trackClick(): void
        -isUniqueClick(): boolean
    }

    class RateLimiter {
        +string key
        +number limit
        +Date windowStart
        +number currentCount
        -canProceed(): boolean
        -increment(): void
        -reset(): void
    }

    ShortenedUrl "1" -- "1" ClickStatistics : has
    ClickStatistics "1" -- "*" RateLimiter : uses

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Optional Enhancements

1. Advanced Features

   • Custom short codes
   • URL expiration
   • Batch URL processing
   • Redis caching implementation

2. Monitoring & Logging

   • Implement request/response logging
   • Add performance monitoring
   • Set up error tracking

Submission Guidelines

1. Fork this repository to your GitHub account
2. Complete the implementation
3. Ensure all tests pass
4. Document your solution in SOLUTION.md
5. Submit the pull request with your changes

Evaluation Criteria

Your solution will be evaluated based on:

1. Code Quality

   • Clean and maintainable code
   • Proper TypeScript usage
   • Comprehensive error handling
   • Code documentation

2. Architecture

   • Proper separation of concerns
   • Scalable design
   • Security considerations

3. Testing

   • Test coverage
   • Test quality
   • Performance benchmarks

4. Documentation

   • Code documentation
   • API documentation
   • Setup instructions