Art of Codeartofcode
Lesson 5 of 21

1. How to Approach a Design Question

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The picture to keep in your head
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1.1 What is a system design interview, and what isn't it?
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1.2 What is the interviewer actually scoring?
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1.3 What's the step-by-step framework?
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1.4 How do you manage a 45-minute round?
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1.5 What questions should you ask first?
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1.6 What's the difference between functional and non-functional requirements?
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1.7 What's an API, and why define it before drawing boxes?
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1.8 How do you sketch the data model?
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1.9 What does a good high-level design look like?
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1.10 How do you choose what to deep dive into?
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1.11 How do you talk about trade-offs?
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1.12 What if you get stuck or don't know something?
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1.13 What are the most common mistakes?
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1.14 What does the bar look like: fresher vs SDE-2?
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Memory card and where the analogy breaks
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Practice: five levels
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Interview questions
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Solutions
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Sources
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Code lab
1. How to Approach a Design Question

1.4 How do you manage a 45-minute round?

3 min read+10 XP

At the architect's desk: If the architect spends the whole meeting choosing tiles for the bathroom, the family leaves without a floor plan. Time goes to the big picture first, details last.

In the interview: A typical split for a 45-minute round:

a 45-minute round: READ first, then Draw, Dive, Defend.

Figure: a 45-minute round. Over a third of it goes by before the main diagram, and that's on purpose.

StepTimeDone when...
Requirements~5 minBoth lists are written down and the interviewer agrees
Estimates~5 minYou have requests per second and storage, roughly
API + data model~10 minMain endpoints and main tables are on the board
High-level design~10 minEvery requirement has a path through your boxes
Deep dive~10 minThe hardest part is solved properly
Trade-offs + wrap-up~5 minYou've named the costs and what you'd do next

Rounds differ. Some are 60 minutes, and some interviewers jump straight to a deep dive. The split is a guide, not a law. What matters is that you never run out of time with no high-level design on the board. A complete simple design beats half of a brilliant one.

One habit that saves you: at each step, say "Does this look right before I move on?" It keeps the interviewer with you and stops you going ten minutes down the wrong road.

Memory code: "5, 5, 10, 10, 10, 5." Requirements, estimates, API and data, high-level, deep dive, wrap-up. Floor plan before the bathroom tiles.