## Scenario You own (or significantly contribute to) a production **fraud detection** system that flags transactions/users as *fraud* vs *legit*. - The model outputs a fraud probability score \(p(\text{fraud})\). - A decision threshold determines whether to **block**, **step-up verify**, or **send to manual review**. - Labels may be delayed (chargebacks) and the data is **highly imbalanced**. ## Questions 1. **Precision/Recall management:** What concrete methods have you used (or would you use) to **measure, manage, and optimize precision and recall** in a real fraud system? 2. **False positives:** How would you diagnose and reduce **false positives** (legit users being flagged) without letting fraud through? 3. **Sudden fraud spike:** If you suddenly observe **many more fraud cases** than usual, what changes would you make (model, thresholding, monitoring, operations), and how would you validate them quickly? 4. **Specific fraud pattern:** If fraud shows a **very specific/pattern** (e.g., a new attack vector with clear signatures), what would you do—rules, model features, segmentation, retraining—and how would you prevent overfitting to a short-lived pattern? Please be explicit about: - The **primary metric** vs **diagnostic metrics** vs **guardrails** you would use. - How you handle **cost asymmetry** (FP vs FN), **label delay**, and **distribution shift/adversarial adaptation**. - The trade-off between **product/user experience** and **fraud loss**.