Senior Full Stack Engineer - Payments

Role Description

You will build across the payments platform: the embeddable SDK that collects card and wallet credentials, the services that create sessions and route transactions to the right gateway, the tokenization boundaries that keep sensitive card data out of our systems, and the webhook and reconciliation flows that keep money accurate. This is not a role about building forms and CRUD screens. It is infrastructure that real money flows through, where a bug is not a broken layout but a failed transaction, a double charge, or a compliance incident. You will work both sides of the wire, and you need to be genuinely strong on both.

What You'll Be Building

• The payment SDK and client layer. Hosted-fields integration with iframe isolation, a gateway-agnostic API so integrators write one integration regardless of processor, and the client-side state model for declines, 3DS, retries, and timeouts.
• The payment services. Session intent and gateway routing, tokenization boundaries, idempotency, HMAC-signed request flows, and the webhook and reconciliation logic that guarantees correctness.
• The platform around it. Versioning and deprecation so we evolve without breaking live merchants, observability across the payment path, and the developer experience for the engineers who integrate against us.

Qualifications

• 7+ years building production software across frontend and backend.
• Strong React and TypeScript. Not "I use React." You understand rendering behavior, state boundaries, effect lifecycles, and how to design a component API other engineers consume.
• Strong backend. .NET and React are our core stack. You can design services, reason about API contracts, debug across the stack, and hold your own in an architecture discussion.
• Payment systems experience. Gateway APIs, tokenization, hosted fields, webhooks, reconciliation, or equivalent work in a domain where correctness is non-negotiable.
• Security fundamentals as instinct. Same-origin policy, CSP, CORS, XSS vectors, iframe isolation, token handling, why secrets never live in client bundles.
• Agentic AI in your workflow. You use Claude Code, Cursor, Codex, or equivalents as a daily driver, not a novelty. We build AI-native and expect you to move at that speed.
• Testing discipline. You write tests because untested payment code is a liability, not because a policy says to.

Requirements

• Java, Kotlin, and Quarkus experience — strongly preferred.
• Hands-on experience with gateway and tokenization stacks.
• PCI DSS scope reduction, SAQ A or SAQ A-EP work.
• 3D Secure 2 implementation.
• Cloud and DevOps exposure (Azure or AWS), CI/CD ownership.

How We Work

We move fast and requirements change. You will not get a fully specified ticket handed to you. You will get a problem, the business context behind it, and the autonomy to solve it.

• You ask the sharp question before writing code, not after shipping the wrong thing.
• You escalate ambiguity early instead of guessing quietly.
• You push back when an approach is wrong, with a better alternative.
• You are comfortable working directly with product and client stakeholders.
• You do not need to be managed into producing work you are proud of. If you have only worked in environments with detailed specs, dedicated QA, and long review cycles, you will find this uncomfortable. If you have worked in startups or fast-moving product teams, this will feel familiar.

The Bar

We are explicit about this because it saves everyone time.

We are hiring for craft. That means naming things well, keeping abstractions honest, deleting code that should not exist, reading the gateway documentation rather than guessing, and caring what the integration feels like for the engineer on the other side. We would rather ship one correct payment flow than five that mostly work.

If that sounds like unnecessary perfectionism, we are not a fit. If it sounds like how software should have been built all along, we want to talk.