Uber·Data Scientist·Technical Phone Screen
Apr 2026
Uber DS interview focused almost entirely on CTR prediction for ads, and it went deep fast. Five interconnected questions covering modeling, imbalance handling, evaluation metrics, calibration, and production validation. The kind of loop where you realize halfway through that they actually want you to know this stuff cold.
- You're building a model to predict whether an ad impression leads to a click within 24 hours. The positive rate is around 0.7%. Propose two model families suited for extreme class imbalance and high-cardinality sparse features. How would you encode ad_id and campaign_id without leaking information, and what does your cross-validation scheme look like given that some click labels arrive up to 24 hours late?
- Compare class weighting, focal loss, undersampling, and calibrated thresholding for handling severe class imbalance. In what situation would you avoid synthetic oversampling, and how do each of these choices affect ranking performance versus calibration?
- Model A has ROC-AUC of 0.91 and PR-AUC of 0.14. Model B has ROC-AUC of 0.88 and PR-AUC of 0.22. Why can these metrics disagree at 0.7% prevalence, which model would you trust for ad CTR prediction, and how do you use a cost matrix around missed clicks versus wasted impressions to pick an operating threshold?
- How would you assess and fix model calibration using isotonic regression versus Platt scaling? Walk through selecting a threshold to maximize F1 versus one that maximizes expected profit. How do you compute precision at the top 1% of scores and use it to compare models?
- Design a bucket test to validate whether the model's scores actually lift CTR in production using a top-k targeting setup. What logs do you need to detect covariate drift and label delay, and how do you prevent feedback loops from corrupting future training data?
“This was the opener and it set the tone.” The rest of the author's notes on Data Scientist interview at Uber, Technical Phone Screen round, covers how they worked through the question, what the panel pushed back on, and what they would do differently.
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