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Amazon·Data Scientist·Technical Phone Screen·Senior

Senior
May 2026

Summary

Amazon data scientist interview with a meaty ML question about building a marketing prediction model. One question but it had a lot of moving parts, felt like they wanted to see if you could hold the whole pipeline in your head at once.

Questions Asked (1)

Q1

You're building a model to predict marketing outcomes. Walk through how you'd use gradient-boosted trees for this, including training, hyperparameter tuning, and evaluation. Also, how do you approach feature selection when you're starting with a large candidate feature set?

Technical Trade-offsProduct Analytics & MetricsAlgorithms & Data Structures
Author's notes

This is deceptively broad.

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AI HintsAI Generated

Suggested Approach

Start by framing the problem in terms of Amazon's marketing context, then walk through a structured pipeline: data preparation, model training with gradient-boosted trees (e.g., XGBoost/LightGBM), hyperparameter tuning via cross-validation, and evaluation using appropriate metrics. For feature selection, emphasize a combination of domain knowledge, statistical methods, and model-based importance, while addressing scalability and potential leakage.

Pro tip: Tie your choices to business impact—e.g., how the model will be used to optimize marketing spend—and mention practical constraints like training time and interpretability, which are valued at Amazon.

1. Problem Framing and Data Preparation

Clarify the prediction goal (e.g., conversion, ROI) and ensure data quality, handling missing values, and encoding categorical variables. Split data temporally to avoid leakage, especially for time-series marketing data.

2. Model Training with Gradient-Boosted Trees

Choose a GBT implementation (XGBoost, LightGBM, CatBoost) based on speed and categorical handling. Start with a baseline model, then iteratively add features and monitor performance.

3. Hyperparameter Tuning

Use Bayesian optimization or random search with cross-validation to tune key parameters like learning rate, max depth, subsample, and regularization. Prioritize parameters by impact and consider early stopping.

4. Evaluation and Validation

Select metrics aligned with business goals (e.g., AUC, lift, precision@k). Use holdout sets and cross-validation, and analyze feature importance and SHAP values for interpretability.

5. Feature Selection Strategy

Start with domain knowledge to filter features, then use statistical tests (e.g., mutual information) and model-based importance (e.g., gain, permutation) to reduce dimensionality. Consider regularization and recursive feature elimination.

Key Points to Mention

  • Handling class imbalance and temporal aspects in marketing data
  • Choice of GBT library and rationale (e.g., LightGBM for speed, CatBoost for categoricals)
  • Hyperparameter tuning techniques: grid search, random search, Bayesian optimization
  • Evaluation metrics beyond accuracy: AUC, lift, precision-recall, business KPIs
  • Feature selection methods: filter, wrapper, embedded, and importance-based
  • Avoiding data leakage and overfitting through proper validation

AI-generated suggestions, not part of the candidate's original notes. May be inaccurate — verify before relying on them.