wbd-system-design-interview

Use the 6-step framework: Requirements (5 min), API (5 min), Data Model (5 min), High-Level Design (10 min), Deep Dive (15 min), and Trade-offs (5 min). Start with an opening monologue that asks clarifying questions and states your plan before drawing anything.

Run three timed drills: design TinyURL (25 min), design a Twitter feed (25 min), and design a chat app (20 min). Apply the same framework to each, then self-score with the 5-point rubric covering clarifying questions, API design, architecture, trade-offs, and narration.

Fan-out-on-write pushes each tweet to every follower's timeline cache, making reads cheap but writes expensive for celebrities. Fan-out-on-read queries at read time, making writes cheap but reads slow. Production systems typically use a hybrid of both.

No. Run the timed drills first so the framework gives you a structure that makes patterns from books like System Design Interview Vol 1/2 stick afterward. Reading first leaves you with facts in a vacuum and no interview tempo.

State the trade-off out loud even without knowing the answer, name what you would want to know more about, or defer the question and finish the current section. Honest recovery beats bluffing, which interviewers can detect.