A Simple Framework for Your First System Design Interview

A system design interview has no single correct answer, which is why it feels hard. What interviewers look for is a clear process. If you follow the same steps every time, you will stay calm even when the problem is new.

• Clarify the requirements. Ask who the users are, what the main features are and what scale you should plan for. Write the functional and non-functional requirements down.

• Sketch the high-level design. Draw the clients, API layer, services and database. Keep it simple and explain how a request flows through the system.

• Choose the data model. Decide what you store and whether a relational or key-value database fits better. Explain why.

• Handle scale. Discuss caching, load balancing and how you would split data as traffic grows.

• Talk about trade-offs. Mention what could fail and what you would improve with more time.

Practise this framework on common prompts like a URL shortener or a chat app. Saying it out loud matters, so try a system design mock interview and get feedback on how clearly you explain each step.