Senior Backend Engineer (L3) - Payments

About Us OpenFX is on a mission to move money as freely as data, unrestricted by time zones, banking hours, or legacy systems. We are building the infrastructure that will power the next generation of cross-border payment systems for institutions. The team's execution has been exceptional, and we're scaling at a remarkable pace. Our stellar early team comes with experience in companies like J.P. Morgan, Goldman Sachs, FalconX, PayPal, Affirm, Polygon, Kraken, Nium & others. We're backed by Accel, Lightspeed, NfX and other top-tier investors. Role Overview We're hiring a backend-heavy Full Stack Engineer for our Payments team — the team that owns how money actually moves for our clients. Payments owns corridor expansion (EUR, MXN, COP, AED, and beyond), the operationalization of our EU licenses (safeguarding of customer funds, transaction monitoring), and the payments product across GUI and API. Our north star is payment volume moved reliably, with corridor success rate and on-time settlement as the control metrics. You will own the systems on that money path. This is where a client's payment gets initiated, routed to the right partner, tracked through cut-offs and settlement, and reconciled — and where a failure is not a bug ticket but stuck money. You will own the backend of these flows — partner integrations, payment lifecycle state machines, webhooks, retries, and idempotency — and be trusted with the correctness of what actually happens to the money. You will also work across the stack. The payments product ships on both API and GUI surfaces, and you'll build the dashboard views your backend powers — payment status, tracking, reporting — rather than waiting on someone else to unblock you. You don't need deep frontend expertise for this role, but you do need to be genuinely comfortable there. We're specifically looking for someone with a payments or fintech background. Think a payment gateway, PSP, neobank, or cross-border payments company (Razorpay, Juspay, Cashfree, PhonePe, Nium, or similar). Key Responsibilities Own the backend of critical payment flows — initiation, partner routing, lifecycle state (statuses, webhooks, returns, recalls), and settlement tracking — across API and GUI surfaces. Build and extend partner integrations for new corridors: adapters for banking and payment partners, cut-off and calendar handling, and reconciliation hooks from day one. Design for correctness under failure — idempotency, safe retries against external partners, exactly-once effects on money state, and graceful degradation when a partner is down. Contribute to the engineering of regulated controls: safeguarding flows and transaction monitoring pipelines, with audit trails built in rather than bolted on. Build the client-facing surfaces your backend powers — payment tracking, status views, and reporting in the dashboard — and ship features end-to-end rather than stopping at the boundary. Instrument the money path — payment…