Design robber detection from surveillance video
Company: Capital One
Role: Data Scientist
Category: Machine Learning
Difficulty: easy
Interview Round: Technical Screen
You’re a Data Scientist on a team building a computer-vision system for public-safety monitoring.
## Problem
Design an ML system that uses fixed surveillance cameras to **detect potential robbers in real time** and trigger an alert to a human operator.
## What to cover
1. **Define the task precisely**
- What is the model predicting (e.g., “robbery in progress”, “person-of-interest”, “weapon present”, “suspicious behavior”)?
- What is the unit of prediction (frame, clip, track, event) and decision thresholding?
2. **Data & labeling strategy**
- Data sources (historical footage, staged data, public datasets) and how you will label positives/negatives.
- How you’ll handle **rare events**, noisy labels, and ambiguous cases.
3. **Modeling approach**
- Candidate pipelines (detection + tracking + action recognition, multimodal, temporal models, etc.).
- How you will deal with occlusion, lighting, camera angle differences, and domain shift.
4. **Evaluation plan**
- Choose **primary metric(s)** and explain tradeoffs (e.g., precision/recall, false alarm rate per hour, detection latency).
- Offline evaluation vs online evaluation; how you’d estimate performance under class imbalance.
5. **Deployment & monitoring**
- Latency/throughput constraints, edge vs cloud inference, model updates.
- Monitoring for drift and performance regression.
6. **Risk, fairness, and privacy**
- Potential harms (misidentification, demographic bias, privacy violations).
- Mitigations, governance, and human-in-the-loop design.
Assume you can ask clarifying questions about operational constraints (camera FPS, compute budget, allowable false alarm rate, legal/privacy requirements).
Quick Answer: This question evaluates applied machine learning and computer vision system-design skills, including precise task definition, data and labeling strategy for rare events, temporal modeling, deployment constraints, and ethical risk assessment.