Software Engineer, Fraud

Join the Future of Commerce with Whatnot!

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. With hubs in the US, UK, Germany, Ireland, Poland, and Australia, 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.

Role

The Fraud Experience team builds intelligent, real-time systems that safeguard Whatnot's marketplace from malicious activity. We design, develop, and deploy end-to-end, ML-driven systems that proactively identify and mitigate fraud blending real-time detection with transparent, user-centered enforcement.

What You'll Do

• Lead the full architecture of fraud detection, prevention, and intervention systems spanning machine learning, backend, and client-side components.
• Build intelligent user graphs to model behavioral patterns, detect collusion networks, and uncover account connectivity at scale.
• Design, train, and deploy both traditional ML and LLM-powered models to detect fraudulent activity across users, payments, and marketplace interactions.
• Develop scalable data pipelines and real-time inference systems capable of supporting high-volume, low-latency ML workloads.
• Create human-in-the-loop systems that continuously refine detection accuracy and adapt to evolving adversarial tactics.
• Perform deep behavioral and adversarial data analysis to surface emerging fraud trends and drive continuous system improvement.
• Stay ahead of the curve by translating new insights into adaptive, production-ready systems that evolve as fast as our adversaries.

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 Los Angeles, New York, San Francisco or Seattle hub.

You 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.

As our next Software Engineer in Fraud team, you should bring 4+ years of software development experience in high-growth environments, along with a strong bias toward action and impact.

What You'll Bring

What Sets You Apart

Benefits

Home office setup allowance

Monthly allowance for wellness

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!).

16 weeks of paid parental leave + one month gradual return to work

EOE

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.