Mock Interview Prompt 001: URL Shortener

Prompt

Design a URL shortening service similar to Bitly.

Interviewer Notes

If the candidate gets stuck, guide them toward:

• short code generation
• redirect-heavy traffic patterns
• caching hot URLs
• database sharding
• analytics as a secondary pipeline

Optional Follow-Ups

• Support custom aliases
• Add expiration time for links
• Prevent abuse and malicious URLs
• Track click analytics by region and device
• Design for global low-latency redirects

What Strong Answers Usually Cover

• requirement clarification
• read-heavy workload
• unique ID generation and Base62 encoding
• cache-first redirect path
• storage schema for short_code -> long_url
• trade-off between relational and NoSQL storage
• 301 vs 302 redirect discussion