Machine Learning Engineer, Fraud

Whatnot is the largest live shopping platform in North America and Europe to buy, sell, and discover the things you love. We’re re-defining e-commerce by blending community, shopping, and entertainment into a community just for you. As a remote co-located team, we’re inspired by innovation and anchored in our values. With hubs in the US, UK, Germany, Ireland, and Poland, we’re building the future of online marketplaces –together.

From fashion, beauty, and electronics to collectibles like trading cards, comic books, and even live plants, our live auctions have something for everyone.

And we’re just getting started! As one of the fastest growing marketplaces, we’re looking for bold, forward-thinking problem solvers across all functional areas. Check out the latest Whatnot updates on our news and engineering blogs and join us as we enable anyone to turn their passion into a business, and bring people together through commerce.

• Design, train, and deploy both traditional ML and LLM-powered models to detect fraudulent behaviors across users, payments, and marketplace interactions.

• Lead the end-to-end architecture of fraud detection, prevention, and intervention systems — balancing platform security with a seamless user experience.

• Build intelligent user graphs to model behavioral patterns, collusion networks, and account connectivity.

• Develop scalable data pipelines and real-time inference systems supporting high-volume, low-latency ML workloads.

• Conduct deep behavioral and adversarial data analysis to uncover fraud trends and continuously improve detection accuracy.

• Partner cross-functionally with Trust & Safety, Payments, and Infrastructure teams to develop features, labels, and model evaluation pipelines.

• Implement model monitoring and drift detection systems to ensure reliability and responsiveness.

• Contribute to fraud risk orchestration, combining rules, models, and heuristics for decision automation.

• Define and track key metrics and dashboards for fraud detection effectiveness (e.g., precision, recall, false-positive rate, latency).

• Stay ahead of emerging fraud tactics and continuously translate insights into adaptive, production-ready systems.

We offer flexibility to work from home or from one of our global office hubs, and we value in-person time for planning, problem-solving, and connection. Team members in this role must live within commuting distance of our SF, NYC, LA OR SEA hubs.

Curious about who thrives at Whatnot? We’ve found that embodying a low ego, growth mindset, and high-impact drive goes a long way here.

• Bachelor’s degree in Computer Science, a related field, or equivalent work experience.

• 2–6 years of experience in machine learning or software engineering, ideally in risk, fraud, or trust & safety domains.

• Strong proficiency in Python and ML libraries (e.g., scikit-learn, PyTorch, LightGBM).

• Solid backend development skills and experience deploying ML models to production (batch or real-time).

• Experience in data analysis and ETL (SQL, Spark, DBT) for data pipeline building.

• Familiarity with fraud detection techniques such as chargeback prediction, anomaly detection, or graph-based modeling.

• Experience with data orchestration frameworks (Dagster, Kubeflow) and feature store design.

• Ability to translate business risk into measurable ML solutions and collaborate across diverse

• Generous Holiday and Time off Policy

• Health Insurance options including Medical, Dental, Vision

• Work From Home Support

  • Home office setup allowance

  • Monthly allowance for cell phone and internet

• Care benefits

  • Monthly allowance for wellness

  • Annual allowance towards Childcare

  • Lifetime benefit for family planning, such as adoption or fertility expenses

• Retirement; 401k offering for Traditional and Roth accounts in the US (employer match up to 4% of base salary) and Pension plans internationally

• Monthly allowance to dogfood the app

  • All Whatnauts are expected to develop a deep understanding of our product. We're passionate about building the best user experience, and all employees are expected to use Whatnot as both a buyer and a seller as part of their job (our dogfooding budget makes this fun and easy!).

• Parental Leave

  • 16 weeks of paid parental leave + one month gradual return to work *company leave allowances run concurrently with country leave requirements which take precedence.

Whatnot is proud to be an Equal Opportunity Employer. We value diversity, and we do not discriminate on the basis of race, religion, color, national origin, gender, sexual orientation, age, marital status, veteran status, parental status, disability status, or any other status protected by local law. We believe that our work is better and our company culture is improved when we encourage, support, and respect the different skills and experiences represented within our workforce.