System Design Interview Blueprint

A candidate sits down for a 45-minute system design interview. The prompt is straightforward: "Design a URL shortening service." Within thirty seconds, the candidate is sketching boxes on the whiteboard — a load balancer, an application server, a database, a cache layer. By the five-minute mark, the whiteboard is covered in arrows and component names.

At minute twelve, the interviewer asks: "How many URLs per day do you expect?" The candidate hesitates. "A lot?" The interviewer tries again: "Should shortened URLs expire? Do users need analytics on click counts?" The candidate realizes the architecture on the board assumes answers to all of these questions — answers that were never discussed.

The candidate knew enough distributed systems to draw a plausible architecture. The interview failed because the first five minutes were spent on boxes and arrows instead of questions and constraints. This book gives you the process to get those first five minutes right.