URL Shortening Service (Case Study)

A URL shortening service with complete CRUD operations, Redis caching for performance, and rate limiting for protection against abuse.

Example Usage

Original URL: https://unsplash.com/photos/a-bull-with-large-horns-eating-grass-in-a-field-0XKM4QW5WUg
Shortened URL: http://localhost:5000/M2v33V

🚩 Problem

Long URLs are:

• Hard to share on social media
• Difficult to remember
• Ugly in print materials
• Not trackable

Existing solutions often lack:

• Full URL management capabilities
• Performance optimization
• Abuse protection

🎯 Goal

Build a URL shortening service that:

• Generates short, memorable URLs
• Redirects quickly with low latency
• Allows full URL management (CRUD)
• Handles high traffic efficiently
• Protects against abuse

✅ Solution

I built a performant URL shortening service featuring:

• Fast URL shortening and redirection
• Redis caching for quick lookups
• Rate limiting for abuse prevention
• Full CRUD operations
• Containerized deployment

🧱 Core Features

URL Operations

• Shorten URL - Transform long URLs into short, shareable links
• Redirect - Seamlessly redirect to original URL
• Update - Modify the original URL for existing short links
• Delete - Remove short URLs when no longer needed
• Get Original - Retrieve the original URL from a short link

Performance & Security

• Redis Caching - Fast lookups for frequently accessed URLs
• Rate Limiting - Protect against abuse and spam
• Request Logging - Morgan for comprehensive request logs

Infrastructure

• Docker & Docker Compose - Easy containerized deployment
• MongoDB - Persistent URL storage
• Redis - High-speed caching layer

🏗 Architecture

┌─────────────┐
│   Client    │
└──────┬──────┘
       │
       ▼
┌─────────────┐
│  Express.js │
│   Server    │
└──────┬──────┘
       │
   ┌───┴───┐
   ▼       ▼
┌──────┐ ┌───────┐
│Redis │ │MongoDB│
│Cache │ │  DB   │
└──────┘ └───────┘

🔧 Tech Stack

Runtime & Framework

• Node.js
• Express.js

Database

• MongoDB (persistent storage)
• Redis (caching layer)

Monitoring

• Morgan (request logging)

Infrastructure

• Docker

🔁 Data Flow

Shortening Flow

1. User submits long URL
2. Generate unique short code
3. Store in MongoDB
4. Cache in Redis
5. Return short URL

Redirect Flow

1. User visits short URL
2. Check Redis cache
3. If miss, query MongoDB
4. Update cache
5. Redirect to long URL

⚙️ Key Technical Challenges

Unique Code Generation

Need short, unique, URL-safe codes.

Solution:
Base62 encoding with collision detection and retry logic.

Low Latency Redirects

Redirects must be fast for good UX.

Solution:
Redis caching with cache-aside pattern.

Abuse Prevention

Service vulnerable to spam and abuse.

Solution:
IP-based rate limiting with configurable thresholds.

Cache Consistency

Cache must stay in sync with database.

Solution:
Write-through caching with TTL-based expiration.

📈 Result

• Sub-10ms redirect latency (cached)
• Handles thousands of requests/second
• Full CRUD API
• Production-ready containerization

💡 Learnings

• Redis dramatically improves read performance
• Rate limiting is essential for public APIs
• Base62 provides good balance of length and uniqueness
• Docker simplifies development and deployment

🔮 Future Improvements

• Click analytics and tracking
• Custom domains
• QR code generation
• Link expiration
• User authentication

🔗 Links

• GitHub Repository

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