Shortify - Scalable URL Shortener

Shortify is a scalable backend URL shortening platform built with Java and Spring Boot.
It focused on implementing real-world system design & backend engineering concepts including: The project focuses on concepts such as:

• Redis-based counters generation
• REST APIs
• Redis caching
• Rate limiting
• URL expiry handling
• Scalable architecture design
• high-performance URL redirection etc.

---

Features

Core Features

• Short URL generation
• URL redirection
• Expiry support
• Unique short links for every request

Backend Engineering Features

• Redis-based distributed atomic counter
• Cache-aside pattern using Redis
• Per-IP rate limiting using Bucket4j
• Base62 encoding
• PostgreSQL persistence
• Non-predictable short code generation

---

Tech Stack

Technology	Purpose
Java 21	Backend Language
Spring Boot	Backend Framework
PostgreSQL	Persistent Database
Redis	Caching + Distributed Counter
Bucket4j	Rate Limiting
Maven	Dependency Management

---

Architecture

The application follows a layered backend architecture with Redis caching and PostgreSQL persistence.

---

Redis Usage

Redis is used for:

1. Distributed Counter Generation

Used for generating unique short codes atomically.

Example: url_counter -> 125

---

2. URL Caching

Used to reduce database load during redirects.

Example: short:Xa12 -> https://google.com

---

Short URL Generation Flow

Client Request
      ↓
Redis Atomic Counter
      ↓
Base62 Encoding
      ↓
Random Prefix Added
      ↓
Persist to PostgreSQL
      ↓
Return Short URL

---

Redirect Flow

GET /{shortCode}
        ↓
Check Redis Cache
        ↓
Cache Hit -> Redirect
        ↓
Cache Miss -> PostgreSQL Lookup
        ↓
Store in Redis
        ↓
Redirect User

---

Rate Limiting

Implemented per-IP rate limiting using Bucket4j.

Limits:

• 10 requests per minute per IP

Purpose:

• Prevent abuse
• Avoid API flooding
• Protect backend resources

---

API Endpoints

Create Short URL

POST /api/v1/urls

Request:

{
  "url": "https://google.com",
  "expiryInDays": 7
}

Response:

{
  "shortUrl": "http://localhost:8080/Xa12"
}

---

Redirect URL

GET /{shortCode}

Redirects user to original URL.

---

Setup Instructions

Clone Repository

git clone https://github.com/GeekyHim/Shortify-URL-Shortner-Project

---

Configure PostgreSQL

Create database:

CREATE DATABASE url_shortener;

Update: src/main/resources/application.properties with database credentials.

---

Run Redis

docker run --name redis-shortify -p 6379:6379 -d redis

---

Run Application

mvn spring-boot:run

---

Future Improvements

• Global exception handling
• Analytics endpoint
• Docker Compose support
• Async analytics processing

---

Learning Outcomes

This project helped in understanding:

• Scalable backend architecture
• Redis caching and distributed counters
• RESTful API design
• Rate limiting and API protection
• Backend performance optimization
• Integration of Redis with Spring Boot
• Designing production-oriented backend services
• Designing systems for reduced database load

It significantly strengthened my practical understanding of backend engineering, System Design, Java Spring Boot, Redis, scalable systems and production-oriented development.