Design a URL Shortener

You're designing a URL shortening service like bit.ly or TinyURL. The system enables users to paste a long URL and receive a short, memorable alias (e.g., https://short.app/abc123). Every shortened link redirects to the original URL. You track click counts for analytics.

Scale assumptions:

• 100 million daily active users (DAU)
• 20% are creators (those who shorten URLs); 80% are readers
• Creators generate ~2 new shortened URLs per day on average
• Readers access shortened links ~5 times per day on average
• Each shortened URL record: ~500 bytes (slug, original URL, metadata)
• Target latency: <100ms for redirect, <200ms for creation
• Availability: 99.95% uptime

Derived numbers:

• New URLs: 100M × 0.2 × 2 = 40M/day ≈ 460 writes/sec average, ~1,500 peak
• Accesses: 100M × 0.8 × 5 = 400M/day ≈ 4,600 reads/sec average, ~15,000 peak
• 5-year URLs: ~73 billion