Expert: Interactive Coding - Payments Processing

At a glance

• Engagement: Independent contractor, fully remote. Live screen-share sessions with our researchers plus short asynchronous write-ups.
• Pay: $60 to $120 per hour. The trial session is paid.
• Commitment: About 10 hours per week, 1 to 3 months to start, with extension for strong performers.
• Start: Rolling
• Location: Remote, any country, with a few hours of overlap with US or EU working hours.

The role

You'll work live with our research team 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, and 3DS/SCA. You implement or review the change the way you would at work, explain your reasoning as you go, tell us where the scenario doesn't match how money actually moves, and help define what correct looks like.

Each session starts from a scenario we provide. You work through it on a shared screen, land the change or the review, and then write a short note on how you approached it. Your work becomes evaluation and training data for frontier models.

You don't need an AI background. You do need to be the kind of engineer who thinks about the duplicate webhook before the happy path, and who knows which rounding rule the ledger expects.

Areas we're hiring for

Each area is defined by the part of the money-movement path you own, so you should fit exactly one. If you work across two, apply under the one where you spend most of your time.

• Payment processing and gateway integration. Engineers who build the checkout and money-movement path: authorization, capture, refund and void flows against a processor or acquirer such as Stripe, Adyen or Braintree, idempotency keys, retries, webhooks and 3DS/SCA. Typical titles: Payments Engineer, Backend Engineer (Payments), Integration Engineer, Checkout Engineer.
• Ledger, settlement and reconciliation. Engineers who own the books behind the payments: double-entry ledgers, settlement files, payout schedules, reconciliation against processor and bank reports, currency handling and rounding. Typical titles: Ledger Engineer, Fintech Backend Engineer, Treasury Systems Engineer, Reconciliation Engineer.
• Disputes, risk and compliance engineering. Engineers who build chargeback and dispute workflows, fraud and risk rules, card-data handling under PCI DSS, and the audit trails behind them. Typical titles: Risk Engineer, Fraud Platform Engineer, Disputes Engineer, Payments Compliance Engineer.

What you'll do

• Implement and review payment flows live with a researcher in a sandboxed codebase: authorization, capture and refund paths, idempotent retries, webhook handlers, ledger entries, reconciliation jobs and dispute handling.
• Explain your reasoning as you work, including the edge cases you check first.
• Review scenarios we have drafted for realism and difficulty, and flag the failure modes that bite real payments teams: double charges, partial captures, currency rounding, race conditions, and stale or replayed webhooks.
• Help write the acceptance criteria for each scenario, including the tempting wrong moves.
• Write short notes after each session on how you approached the problem and what you verified.
• Work in reviewer feedback within agreed turnaround times, and flag guideline gaps or edge cases you run into.

Who we're looking for

Required

• 3+ years writing production code for a payment processor, a processor integration, a card issuer or acquirer, a fintech ledger or a bank's payments platform, including work within the last two years. You wrote the code yourself; managing the team is not enough.
• Working command of the money-movement lifecycle end to end: authorization, capture, settlement, reconciliation and disputes, and the compliance edges such as PCI DSS and SCA.
• Comfortable in at least one of Python, Go, Java or TypeScript, and at reading unfamiliar codebases.
• Able to explain your reasoning out loud while you work, in clear professional English.
• Reliable availability for scheduled live sessions and the habit of showing the evidence behind every conclusion.

Nice to have

• Experience with several processors or rails, such as Stripe, Adyen, card networks, ACH, SEPA or UPI.
• Experience writing technical design documents, incident reviews or interview questions for payments systems.
• Familiarity with how AI coding agents fail on payments work.

Our standards

• All solutions, write-ups and reviews are your own work. LLM-generated code or text is not permitted.
• Scenarios and solutions must be original. Nothing may be copied from published or easily searchable sources.
• Never include code, configuration or transaction data from a current or former employer or client, or anything covered by an NDA. All companies, systems and scenarios are fictional, and all work is your own.
• Quality is judged on correctness, clarity of reasoning and reviewer agreement, not on speed or volume.

How hiring works

• Short AI interview and resume review
• One paid trial session, scored against a fixed quality checklist
• Onboarding and your first project