Staff Software Engineer - PayBox

PayBox is one of MoonPay’s newest products. It enables people to transact directly through AI, connecting agents with payments, wallets and applications without requiring users to hand over their underlying credentials.

We launched PayBox recently and saw strong initial traction. Now we’re building the next phase.

There are multiple major product tracks underway: expanding PayBox across AI platforms, building peer-to-peer payment experiences, integrating with DeFi applications, growing our plugin ecosystem and significantly improving the end-to-end product experience.

We’re looking for an exceptional Staff Software Engineer to help own PayBox and take it through this next stage.

You’ll work closely with our Chief Engineer and a small, highly focused team. This is much closer to a founding engineer role than a traditional Staff engineering position. You’ll be expected to identify what matters, reason through difficult problems, make decisions and take areas of the product from idea through to production.

That could mean designing and building an entirely new PayBox capability one week and obsessing over the details of an onboarding flow the next. We care equally about ambitious technical problems and the less glamorous work required to make a product great.

We’re not looking for a specific technology or domain background. You don’t need previous crypto or MCP experience. We’re looking for an exceptional generalist engineer who can learn quickly, think independently, build end-to-end and deeply cares about what they ship.

What You Will Do

• Own significant areas of PayBox end-to-end, from identifying the problem and defining the approach through to building, shipping and iterating in production.
• Help take a recently launched product through its next phase of 0→1 development and growth.
• Build new payment and peer-to-peer transfer experiences designed for AI interfaces.
• Build integrations across AI platforms, applications and the wider PayBox ecosystem.
• Help develop the infrastructure and product experiences required to bring new applications and integrations onto PayBox.
• Work closely with Product to turn ambitious ideas into simple, usable experiences.
• Sweat the details of the PayBox experience — particularly onboarding and UX — and fix the friction that prevents users from successfully using the product.
• Reason from first principles about difficult technical and product problems, making pragmatic decisions without waiting for perfect information.
• Move across different parts of the product and technical stack depending on where the highest-impact problem is.
• Use AI extensively to increase your speed and output while maintaining your own technical reasoning, judgement and attention to detail.

About You

We’re deliberately not defining the ideal candidate by a particular technology stack or domain.

There are three things we care deeply about: technical ability, motivation and thoroughness. We’re looking for someone exceptional across all three.

Must-have experience and skills

• Exceptional technical reasoning. You have strong engineering fundamentals and can break down unfamiliar, ambiguous problems and reason towards good solutions.
• High agency. You don’t wait for perfectly defined requirements or someone else to identify what needs doing. You find important problems and take responsibility for solving them.
• End-to-end ownership. You’ve built and shipped meaningful products, projects or systems from beginning to end rather than operating within a narrowly defined area.
• Thoroughness. You care deeply about the quality of your work and sweat details others might overlook. Getting something working is the beginning, not the end.
• Strong systems thinking. You can design systems, understand technical trade-offs and make sensible architectural decisions while moving quickly.
• Product judgement. You understand that great engineering includes the experience around the technology, not just the underlying implementation.
• Comfort with ambiguity. You’re at your best in environments where there are more problems than people and priorities can change quickly.
• Independent thinking in an AI-native environment. You use AI aggressively as a tool, but you don’t outsource your reasoning to it. You understand the output, challenge it and remain accountable for what you ship.
• Deep motivation. You want ownership and responsibility and care about the outcome of the product, not simply completing the work assigned to you.

Nice-to-have experience

• Experience as a founding engineer or early engineer at a high-growth startup.
• Experience founding and building your own company or product.
• Experience taking a product from an idea through launch and subsequent iteration.
• Experience operating in small, highly autonomous engineering teams.

Bonus Points

• Experience building AI-native products, agents or developer tooling.
• Experience with payments, fintech, crypto or DeFi.
• Previous experience with MCP or other emerging agent protocols.

None of these are prerequisites. We care considerably more about how you think, what you’ve built, how you operate and how much you care about the quality of your work.