Interactive Coding: Payments Processing (Part-Time, Remote)

We build realistic environments that test how well AI coding agents handle real engineering work. For this project we need engineers who have built or operated payments systems to work interactively with our research team: implement and review payment flows in a sandboxed codebase, tell us where our scenarios don't match how money actually moves, and help define what correct looks like. What you'll do (about 10 hrs/week) - Pair live with our researchers (screen-share) on coding scenarios in a sandboxed payments codebase: authorization, capture and refund flows, idempotency and retries, webhook handling, reconciliation and settlement, ledger entries, chargebacks and disputes, 3DS/SCA, and handling of card data. - Review scenarios we've drafted for realism and difficulty, and flag the failure modes that bite real payments teams: double charges, partial captures, currency rounding, race conditions, stale webhooks. - Help write the acceptance criteria and the tempting wrong moves. - Write short notes on how you actually approached each problem. Who you are - You have written production code for a payment processor, a PSP integration (Stripe, Adyen, Braintree, Checkout.com), a card issuer or acquirer, a fintech ledger, or a bank's payments platform within the last two years. - Comfortable in at least one of Python, Go, Java or TypeScript, and at reading unfamiliar codebases. - Understand the money-movement lifecycle end to end (auth, capture, settlement, reconciliation, disputes) and the compliance edges (PCI DSS, SCA). - Able to explain your reasoning out loud while you work. Logistics - $150 USD/hour, about 10 hours per week, 1-3 months to start with possible extension. Remote, any country. We need a few hours of overlap with US or EU working hours for live sessions. NDA required before work starts. - Please answer the screening questions yourself, without AI assistance; we are hiring for your judgment.