A repeatable five-step framework that beats raw cleverness.
The Interview Method: Clarify → Scope → Sketch → Scale → Summarize: a repeatable five-step fram...
frame the problem before drawing the system
Hash-of-URL ID is deterministic but invites collisions.
Most candidates fail system design interviews not because they lack knowledge but because they have no method — they free-associate and run out of time. A simple five-step loop solves this: Clarify the problem, Scope the cut you'll design, Sketch the high-level picture, Scale each component under load, Summarize tradeoffs.
Clarify (~5 min). State what you heard, then ask questions that change the design: who uses it, what scale, what is in scope, what isn't. Avoid trivia like 'what color is the button.'
Scope (~3 min). Pick 3–5 functional requirements you'll actually design. Name what you're cutting. This is where you avoid boiling the ocean.
Sketch (~10 min). Draw a clean high-level picture: client, edge, app, data. Pick a happy path and trace one request through it end to end.
Scale (~20 min). For each component on the path, walk through what breaks at 10x and 100x — and how you'd fix it. Do real estimation here.
Summarize (~5 min). Restate what you built, list the top 3 tradeoffs, and name what you'd revisit with more time. This is the single highest-leverage 5 minutes.
Interviewer: 'Design a URL shortener.'