My system design round is in six weeks and I still don't understand what "there's no wrong answer" is supposed to mean
Every prep resource says the same thing — there's no single right design, they're evaluating how you think. Cool, except when I sit down and start drawing boxes I freeze because I don't know which tradeoff they actually want me to defend. Load balancer here or there, cache invalidation strategy, do I even mention sharding unless asked. I've read the classic write-ups on URL shorteners and rate limiters and I can recite them, but the second someone changes one constraint I'm lost. For people who've actually passed these — what does "good enough" reasoning sound like out loud, not on paper?
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AnonymousAnon Following up on the metric idea — do you actually say which metric you're picking out loud at the start, or let the interviewer infer it from your design choices? I've been doing the second and wondering if I should just state it explicitly up front.
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AnonymousAnon The thing that helped me most was stopping trying to design the 'right' system and instead picking one metric to optimize for out loud — latency, cost, availability — and defending every choice against that one thing. Interviewers seem to care way more about consistency of reasoning than the actual boxes.