System Design Interview Prep for Mid-Level Developers
System design rounds trip up even experienced devs. This guide breaks down what interviewers actually want and how to structure your answers.
Clarify requirements before drawing anything
Spend the first 5 minutes asking about scale, constraints, and priorities. Interviewers reward structured thinking over jumping straight to a solution.
Start with a high-level diagram
Sketch a basic architecture: client → load balancer → app servers → database. Establish the skeleton before adding detail.
Talk through data storage choices
Explain why you'd choose SQL vs NoSQL, relational vs document. The reasoning matters more than the choice itself.
Address scaling bottlenecks explicitly
Walk through caching strategies (Redis), CDN usage, database sharding, and horizontal vs vertical scaling as the system grows.
Discuss trade-offs openly
Every design decision involves trade-offs. Saying 'I'd use X here because it optimises for Y, though it sacrifices Z' shows senior-level thinking.
You've reached the end of this guide. Now go apply what you've learned!
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