HardSystem designSystem design20 min to answer

Walk me through the system design of an AI-powered user experience.

Asked at

Microsoft

1Give yourself 20 minutes

2Answer out loud, not in your head

3Then compare with the answer below

Stuck? Show a way to structure it+

01Clarify the objective, user, constraints, and acceptable failure modes.
02Structure the response around user flow, model layer, evaluation, fallbacks.
03Compare credible alternatives and state the decision criteria.
04Finish with validation, monitoring, and what would change the decision.

Reference answer

strong answer

I would first define the outcome and acceptable error boundary. I would explicitly cover user flow, model layer, evaluation, fallbacks. I would select an approach only after comparing quality, latency, cost, safety, and operational complexity, then validate it with representative cases and production monitoring.

user flow
model layer
evaluation
fallbacks

Must be adapted to the interviewer’s scenario
Would benefit from concrete numbers and personal examples

alternative answer

A second valid approach is to begin with the highest-risk assumption and test it cheaply. I would explicitly cover user flow, model layer, evaluation, fallbacks. I would select an approach only after comparing quality, latency, cost, safety, and operational complexity, then validate it with representative cases and production monitoring.

user flow
model layer
evaluation
fallbacks

Must be adapted to the interviewer’s scenario
Would benefit from concrete numbers and personal examples

Grade yourself

user flow

weight 30%

StrongExplains user flow concretely and ties it to a decision or measurable outcome.

WeakMentions user flow without implications, trade-offs, or evidence.

model layer

weight 25%

StrongExplains model layer concretely and ties it to a decision or measurable outcome.

WeakMentions model layer without implications, trade-offs, or evidence.

evaluation

weight 25%

StrongExplains evaluation concretely and ties it to a decision or measurable outcome.

WeakMentions evaluation without implications, trade-offs, or evidence.

fallbacks

weight 20%

StrongExplains fallbacks concretely and ties it to a decision or measurable outcome.

WeakMentions fallbacks without implications, trade-offs, or evidence.

Then expect these follow-ups

Where is the first bottleneck at 10× traffic?
Tests: depth
What are the main failure modes?
Tests: adaptability
How would you roll this out safely?
Tests: adaptability

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