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URL Shortener

A fast URL shortener REST API with nanoid-generated short codes, click tracking, duplicate detection, and rate limiting.

Level: 3  ·  Status: ✅ Built  ·  Live Demo  ·  Source Code

Purpose

URL shorteners are deceptively simple — they teach important concepts: ID generation strategies, redirect mechanics (301 vs 302), click analytics, and handling high-frequency reads (redirect lookups) vs low-frequency writes (URL creation). This project uses nanoid for collision-resistant short codes and SQLite for persistence.

Tech Stack

  • Runtime: Node.js
  • Framework: Express 5
  • Database: SQLite (better-sqlite3)
  • ID Generation: nanoid 5
  • Security: Helmet 8, express-rate-limit
  • Documentation: Swagger (swagger-jsdoc + swagger-ui-express)
  • Deployment: Render.com

Build Steps

  1. Design the URLs table. Schema: id, short_code (UNIQUE), original_url, clicks (DEFAULT 0), created_at. Index on short_code for O(1) redirect lookups. Store the URL in the data/ directory.

  2. Build the shorten endpoint. POST /shorten accepts a URL, validates it (must be a valid URL format), checks for duplicates (if already shortened, return the existing short code), generates a nanoid (7-8 chars), stores it, and returns the short URL.

  3. Implement redirect. GET /:shortCode looks up the original URL by short code. If found, increment the click counter and redirect (302 Found). If not found, return 404. This is the most performance-critical endpoint.

  4. Add click tracking. Every redirect increments a counter. GET /stats/:shortCode returns: original URL, short code, total clicks, and creation date. This provides basic analytics without complex event tracking.

  5. Implement duplicate detection. Before creating a new short URL, check if the original URL already exists in the database. If it does, return the existing short code instead of creating a duplicate. This saves storage and keeps URLs consistent.

  6. Add rate limiting and security. Rate limit the creation endpoint (prevent abuse) but not the redirect endpoint (must be fast). Helmet for security headers. Validate URLs to prevent XSS via malicious redirect targets.

  7. Deploy to Render. SQLite in the data/ directory. No external services needed. Short URLs use the Render domain as the base.

Deployment

Deploy on Render.com. The short URL base is your Render domain. No external database or cache services required.

Tips

  • nanoid generates URL-safe, collision-resistant IDs. At 7 characters with the default alphabet (64 chars), you get ~4.4 trillion possible combinations. Collisions are astronomically unlikely — but check for uniqueness on insert anyway.
  • Use 302 (temporary) redirect, not 301 (permanent). With 301, browsers cache the redirect forever — you can never update or disable the short URL. With 302, every click hits your server (enabling accurate tracking).
  • Extension: add custom short codes (user-chosen aliases), expiration dates, password-protected links, or a QR code generator for each short URL.

README Guidance

The project repo's README should include a description, API endpoints with examples, how redirect works, tech stack, and setup instructions.