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Meta·Data Scientist·Technical Phone Screen·Senior

Senior
Jun 2026

Summary

Meta DS interview with a meaty ML design question about fake news detection. Single question but they clearly wanted you to go broad and then deep, covering features, modeling, and ops. Felt more like a system design round than a typical ML theory quiz.

Questions Asked (1)

Q1

How would you design a machine learning system to automatically detect and flag fake news on Facebook? Walk through the features you'd use, your modeling choices, how you'd evaluate it, and how you'd handle the model degrading over time.

System DesignTechnical Trade-offsProduct Analytics & Metrics
Author's notes

This question is deceptively wide.

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AI HintsAI Generated

Suggested Approach

Start by clarifying the problem scope and success metrics, then walk through the ML lifecycle: data collection, feature engineering, model selection, evaluation, and monitoring. Emphasize trade-offs between precision and recall, and how you'd handle concept drift and adversarial behavior. Conclude with a deployment and feedback loop strategy.

Pro tip: Frame the problem as a ranking and triage system rather than a binary classifier, and discuss how you'd incorporate human-in-the-loop review to balance automation with accuracy. Highlight the importance of explainability for trust and regulatory compliance.

1. Clarify Requirements and Metrics

Define what 'fake news' means, the scale of the problem, and the key metrics (e.g., precision, recall, F1, AUC, or business metrics like user reports). Consider the cost of false positives vs. false negatives.

2. Data Collection and Feature Engineering

Identify data sources (post content, user engagement, source credibility, propagation patterns). Engineer features from text (TF-IDF, embeddings), metadata, and graph-based features (sharing network).

3. Model Selection and Training

Choose models (e.g., gradient boosted trees, deep learning for text, graph neural networks). Address class imbalance, use ensemble methods, and consider multi-modal approaches. Train with cross-validation and handle adversarial examples.

4. Evaluation and Validation

Use offline metrics (precision-recall curves, AUC) and online A/B testing. Incorporate human evaluation and measure real-world impact (e.g., reduction in spread). Consider fairness and bias across demographics.

5. Deployment and Monitoring

Deploy with a feedback loop: flag content for review, collect labels, and retrain periodically. Monitor for drift using statistical tests and performance metrics. Implement safeguards against adversarial attacks and model degradation.

Key Points to Mention

  • Precision vs. recall trade-off and the cost of false positives/negatives in content moderation
  • Feature engineering: text, metadata, user behavior, and graph-based features (e.g., propagation patterns)
  • Model choices: gradient boosting, deep learning (BERT), graph neural networks, and ensemble methods
  • Evaluation: offline metrics, online A/B testing, human-in-the-loop validation, and fairness considerations
  • Handling concept drift: monitoring, retraining, and active learning with human feedback
  • Adversarial robustness: detecting and adapting to evolving fake news tactics

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