A layer-by-layer breakdown of how a request actually moves through a URL shortener — CDN, load balancer, app servers, cache, and database — with separate diagrams for the write path and the read path.
Back-of-the-envelope math for a URL shortener — QPS, storage growth over five years, bandwidth, and cache sizing using the 80/20 rule. The exact numbers interviewers expect you to produce on a whiteboard.
The schema, REST API contracts, rate limiting strategy, and SQL-vs-NoSQL decision for a URL shortener — the implementation details interviewers probe once the high-level architecture is settled.
Everyone can design a URL shortener that works for 10 requests a second. Here's what actually breaks when you hit 10,000 requests a second: database hotspots, cache stampedes, hash collisions, and the geographic latency problem nobody mentions in the whiteboard round.
A complete walkthrough of the URL shortener interview question — requirements gathering, architecture, hash generation strategies, and read-heavy scaling patterns interviewers actually look for.