What I'm seeing is that most people bomb system design interviews because they jump straight into solutions without understanding the problem first. Here's how to actually approach these questions:

Nov 8, 2025 路 12:30 AM UTC

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Start with clarifying questions. Don't assume anything. Ask about scale (how many users?), performance requirements (what's acceptable latency?), and constraints (budget limitations? existing infrastructure?). This shows you think before you build.
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State your assumptions clearly. If the interviewer doesn't give you specifics, make reasonable assumptions and say them out loud.
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"I'm assuming we need to handle 10 million daily active users" or "I'm assuming we need 99.9% uptime." This keeps you aligned with what they're looking for.
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Start high-level, then drill down. Sketch out the major components first. Don't get lost in implementation details immediately.
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Show the big picture: client, load balancer, application servers, databases, caching layer. Then go deeper on the pieces that matter most for the specific problem.
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Talk about trade-offs. Every design decision has pros and cons. SQL vs NoSQL? Monolith vs microservices? Discuss why you're choosing one approach over another.
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"I'd use a relational database here because we need strong consistency for financial transactions, even though it limits our horizontal scaling options."
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Address scalability and reliability. How does your system handle growth? What happens when something fails? Show you're thinking about real-world operation, not just making something work once.
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Communicate constantly. System design interviews are conversations, not coding tests. Think out loud. Ask if you're on the right track. Engage with the interviewer's feedback and adjust your approach.
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The goal isn't to have the perfect answer. It's to demonstrate how you think through complex problems, make decisions, and communicate technical concepts clearly. That's what separates people who pass from people who don't.