Staff Security Engineer, Payments

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.

Payments & Orders at Whatnot build and operate our tier‑0 commerce platforms, powering the full lifecycle of every transaction—from secure pay‑ins and resilient order creation to refunds, ledgering, payouts, and customer‑facing financial reporting—while guaranteeing both financial and referential integrity end‑to‑end. We take a platform‑first approach, providing reusable primitives and APIs for Payment Methods, Orders, Transactions, Payouts, Incentives, and Tax that enable product teams to ship reliably at scale across markets and payment methods, while managing an ever‑growing multi‑billion‑dollar flow of funds across multiple international markets. You’ll partner with core feature teams and the CISO/Security org to drive a rigorous, defense‑in‑depth posture and uphold our high bar for reliability, risk, and compliance. You’ll own meaningful areas, advance the domain in collaboration with leadership, and exercise strong trade‑off judgment and clear communication.

In this role, you will…

• Architect, design and build high-throughput, low-latency solutions for securing the entire financial stack of the business, end to end.

• Define and enforce rigorous security patterns, service contracts, fault-isolation across teams that build on top of the Payments Foundation stack.

• Mentor and guide senior engineers, lead code reviews, design reviews, and promote best practices in system design, testing, observability, and deployment.

• Participate in incident response, root-cause analysis, and post-mortem processes for critical system failures.

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 Dublin hub.

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 Lead Payments Security Engineer, you should have:

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

• We value deep payments security expertise and relevant certifications.

• 8+ years (for Staff) or 10+ years (for Senior Staff) of backend/distributed systems engineering experience.

• Strong security experience across multiple roles. Scar tissue hardening end-to-end business flows and ensuring zero-access principles to any function.

• Strong mastery of distributed systems fundamentals: consensus, partitioning, replication, coordination, sharding, state management, etc.

• Deep experience with high-throughput, low-latency services and stream processing (e.g., Kafka, Flink, etc.).

• Strong software design, algorithmic, and data-structure skills.

• Proficiency in one or more languages (e.g., Python, Go) and scripting.

• Proven track record of leading security and scaling core systems under high load, especially in core commerce and payments systems.

• Excellent communication skills, ability to influence cross-organizational stakeholders.

• Proven track record of delivering features end-to-end and can ship products and features lightning-fast without sacrificing quality.

• Strong ownership instincts — capable of driving projects from inception to production and beyond.

• The ability to pick up on new technologies very quickly.

• Startup experience at a high-growth company — working in fast-paced, rapidly evolving product environments with frequent experimentation (nice to have).

• 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

• 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.

Please find our Whatnot Candidate Privacy Notice here.

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.