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Tech roles · 10 questions
System design discussion
A system-design round is a discussion, not a quiz: interviewers want requirements before boxes, trade-offs before buzzwords, and numbers before adjectives. Each question is a mini-scenario probing one competency. Expect follow-ups, and think out loud.
- 01Requirements & scopingA PM asks you to 'add real-time notifications' to your product. Before designing anything: what do you need to know, and what would you propose as a v1 scope?
- 02API & data modelDesign the API and data model for a link-shortening service. Walk through your choices out loud.
- 03High-level architectureSketch, in words, the architecture for a photo-sharing app expecting a million uploads a day. What are the main components, and why those?
- 04Read-heavy scalingYour product-page database is falling over at 50k reads/sec; writes are trivial. What do you do, and in what order?
- 05Write-heavy & hot keysA voting feature must absorb 200k votes a minute during a live show, and one contestant gets most of them. Design the write path.
- 06Storage trade-offsAn audit-log service must keep seven years of append-only events. Which storage do you pick and why, and what requirement change would flip your choice?
- 07Caching & invalidationYou add a cache in front of the user-profile service and users start seeing stale names after edits. Walk through your invalidation options and what you'd pick.
- 08Failure & resilienceThe payment provider your checkout depends on starts timing out on 5% of requests. What happens in your design today, and what should happen?
- 09Consistency trade-offsTwo users can book the last seat on a flight at the same moment. Where do you enforce consistency, and what do you trade away to get it?
- 10EstimationBallpark the storage and bandwidth for keeping 30 days of activity for ten million daily active users. Talk through the arithmetic.