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This is a medium difficulty Machine Learning question, commonly asked during Onsite rounds at Netflix.

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This question is commonly asked for Data Scientist candidates at Netflix during technical interviews.

Address Fraud Detection with Imbalance and Concept Drift Solutions

Last updated: Mar 29, 2026

Quick Overview

This question evaluates a data scientist's competence in designing end-to-end machine learning systems for fraud detection, emphasizing challenges such as delayed labels, severe class imbalance, and evolving data distributions (concept drift) in near-real-time scoring.

Netflix

Jul 12, 2025, 6:59 PM

Data Scientist

Onsite

Machine Learning

End-to-End ML Workflow: Online Payments Fraud Detection

Scenario

You are designing a fraud-detection system for an online payments product that must score transactions in (near) real time. Labels for fraud (e.g., chargebacks) arrive with delays, fraud is rare (severe class imbalance), and fraud patterns evolve over time (concept drift).

Task

Outline the end-to-end ML workflow, covering:

Data collection and labeling
Feature engineering
Model selection and training
Validation and offline evaluation
Deployment and inference
Monitoring and retraining

Additionally, explain how you would handle:

Severe class imbalance
Concept drift

Note: Discuss techniques such as resampling, cost-sensitive learning, ROC-AUC/PR-AUC, sliding windows, and automated retraining triggers.

Solution

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