Design URL Shortener

Question

Design a URL shortening service like TinyURL.

Requirements:
- Convert long URL to short URL
- Support custom short URLs
- Handle high traffic
- Analytics tracking
- URL expiration

Example: 
Long URL: https://www.example.com/very/long/path
Short URL: http://tiny.url/abc123

Accepted Answer

URL Shortener System Design:

1. Architecture Components:
   - Load Balancer
   - Application Servers
   - Database (Primary-Secondary)
   - Cache Layer (Redis)
   - Analytics Service

2. Core Services:
```typescript
interface URLShortener {
  shorten(longUrl: string): string;
  redirect(shortUrl: string): string;
  customize(longUrl: string, customPath: string): string;
}

class URLService implements URLShortener {
  private readonly baseChars: string;
  private readonly redis: Redis;
  private readonly db: Database;

async shorten(longUrl: string): Promise<string> {
    const id = await this.generateUniqueId();
    const shortPath = this.encode(id);
    await this.store(shortPath, longUrl);
    return this.baseUrl + shortPath;
  }
}
```

3. Database Schema:
```sql
CREATE TABLE urls (
  id BIGSERIAL PRIMARY KEY,
  short_path VARCHAR(10) UNIQUE,
  long_url TEXT NOT NULL,
  user_id UUID,
  created_at TIMESTAMP,
  expires_at TIMESTAMP,
  click_count INTEGER DEFAULT 0
);
```

4. Key Features:
   - Base62 encoding
   - Collision handling
   - Rate limiting
   - Analytics tracking
   - Cache management

5. Scalability:
   - Horizontal scaling
   - Database sharding
   - CDN integration
   - Cache invalidation

Company Context (Meta):
- Focus on scalability
- Real-time analytics
- Global distribution
- Privacy considerations

Design URL Shortener

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