HardSystem designSystem design30 min to answer

Design a production search ranking system from data collection through serving.

1Give yourself 30 minutes

2Answer out loud, not in your head

3Then compare with the answer below

Stuck? Show a way to structure it+

01Clarify objective, users, constraints, and failure tolerance.
02Cover relevance, retrieval, ranking, counterfactual evaluation in a causal structure.
03Compare at least two credible approaches.
04Specify evaluation, rollout, monitoring, and rollback.

Reference answer

strong answer

I would begin by defining the target outcome and acceptable failure boundary. For search ranking: system design, I would analyze relevance, retrieval, ranking, counterfactual evaluation, compare alternatives on quality, latency, cost, and risk, and validate on representative slices before a monitored rollout.

relevance
retrieval
ranking
counterfactual evaluation

Requires scenario-specific numbers
Should include relevant personal experience

alternative answer

I would start with the riskiest assumption in search ranking: system design, create the cheapest discriminating experiment, then use the evidence to choose an architecture and release threshold.

experimentation
risk-first sequencing
decision clarity

Needs deeper implementation detail

Grade yourself

relevance

weight 30%

StrongExplains relevance with mechanisms, trade-offs, and validation.

WeakNames relevance without operational implications.

retrieval

weight 25%

StrongExplains retrieval with mechanisms, trade-offs, and validation.

WeakNames retrieval without operational implications.

ranking

weight 25%

StrongExplains ranking with mechanisms, trade-offs, and validation.

WeakNames ranking without operational implications.

counterfactual evaluation

weight 20%

StrongExplains counterfactual evaluation with mechanisms, trade-offs, and validation.

WeakNames counterfactual evaluation without operational implications.

Then expect these follow-ups

Which assumption is most likely to invalidate your approach?
Tests: depth
What would you measure offline and in production?
Tests: evaluation
How would your answer change with one-tenth the data or compute?
Tests: adaptability

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