Senior Software Engineer, Payments

alt; United States; Remote; USD 180,000 - 240,000; Full time

Job summary

Alt is reshaping the $5B trading-card market by building a real-time, scalable payments platform. You’ll own the money movement layer—from landing funds to ledger reconciliation—across ACH, wires, instant rails, and settlement.

You’ll design for reliability, correctness, and fast payouts in a high-value marketplace. Join a team that defies the status quo, builds orchestration across multiple providers, and ships with an emphasis on fault tolerance, idempotency, and data-driven risk controls.

Responsibilities

• Own Rails and money movement, including ACH origination/returns, RTP, wires, cards, and stablecoin settlement.

Job description

Alt is unlocking the value of alternative assets, starting with the $5 B trading-card market. We let collectors buy, sell, vault, and finance their cards in one place and we are backed by leaders at Stripe, Coinbase, Seven Seven Six, and pro athletes like Tom Brady and Giannis Antetokounmpo. Our next frontier is real-time pricing at scale-the Alt Value that powers every trade, loan, and product on the platform.

The Role

An auction closes and every seller in it gets paid in the same moment, each against a different fee schedule - some by ACH, some by wire, some instant. A buyer funds a five-figure purchase and the bank returns it three days later. A webhook arrives twice, out of order, from a provider that was down for an hour. Every one of those movements has to reach the right account, on the right rail, at the right time, and land in the ledger exactly once.

That is the whole job. You own how money physically moves at Alt: the providers, the rails, the orchestration layer that routes between them, and the risk posture that keeps a marketplace of high-value transactions safe. The ledger team owns the record; you own everything that happens between a customer's bank and that record. You are not building a checkout flow. You are building the liquidity that makes this marketplace work.

The KPI: 99.99% reliability on gateway and banking integrations, and a time-to-funds for sellers and borrowers that we measure, publish, and beat every quarter. In payments, "mostly working" is a failure.

The people who are great at this have integrated a provider that lied to them, and they design for the third retry, the late return, and the duplicate callback because they've been on the wrong side of all three.

What You'll Own

• Rails and money movement. ACH origination and returns, RTP and other instant rails, wires, cards, and stablecoin settlement. A $300K wire and a $300 ACH debit are different products with different controls, and you'll design for both. Credit-push rails change what you can auto-charge and when funds are final - you'll own those product consequences, not just the integration.
• Provider architecture and orchestration. Multi-PSP integrations built so the next one isn't a rewrite, and a single orchestration layer that routes each movement to the right provider by cost, speed, and health. Webhooks, idempotency, retry semantics, state machines, failure modes on the third retry, and provider failover that nobody notices.
• Payouts and collections. Getting sellers and borrowers their money faster than anyone else in this market: instant payout options, batch payouts at auction close, and the rail and timing choices that make them safe. On the other side, cash advance disbursement and the scheduled auto-pay batches that collect repayments run on your rails. The ledger team decides what a pending balance means; you decide how and when the money actually moves.
• Risk on high-value flows. The fraud, dispute, and chargeback posture for a marketplace where one bad transaction is a five- or six-figure problem. Holds, limits, and settlement windows set with data - and you'll know what each one costs in conversion. Step-up verification triggered by risk signals rather than blanket friction.
• Payment operations. When a transfer is stuck, a return code is unfamiliar, or a provider goes quiet mid-batch, you find out why. You'll own the tooling that lets operations and support answer "where is my money" without paging an engineer, and you'll feed clean, complete processor data to the ledger team's reconciliation so their breaks are real breaks and not missing webhooks.
• The posting contract, from the producer side. Every movement you originate lands in the ledger through a typed contract the ledger team owns. You'll build against it, push on it when a new rail doesn't fit, and guarantee exactly-once delivery into it.
• The trade-off calls. Shipping speed against uncompromising reliability; build custom versus buy an orchestration platform. You'll be asked to defend both directions.
• The team. Be a multiplier through rigorous code reviews, technical documentation, and mentorship.

How You'll Use AI Here

We don't want to hear that you use Claude every day. Everyone does. We want to know what you've built with it. Concretely, in this role:

• Turn a payment provider or bank partner integration spec into a typed client and a test suite in an afternoon instead of a sprint - including the ACH return codes and reversal paths nobody wants to hand-write
• Stand up a rail simulator that produces the failures a sandbox won't: a late return, a duplicate callback, a partial reversal, a webhook that arrives twice out of order, a settlement that lands after the window closed. Then run the orchestration layer against it
• Build an agent that watches provider health, webhook lag, and return rates, and proposes a routing change or a hold before the on-call sees the alert
• Put an MCP server over provider APIs and our payment state so 'why did this payout f