Senior Software Engineer, Payments

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 fail" is a question support asks in plain language

• Use models to generate adversarial test cases for the orchestration state machine — the provider that acks and then times out, the failover mid‑batch, the return that hits after the payout cleared — and find the transitions nobody specified

• Use Claude Code or Cursor as the default way you work through a provider migration or a refactor, not as autocomplete

If you've built agents, wired up connectors, written skills or MCP servers, or shipped internal tooling your team actually depends on — lead with that. Name the artifact, not the tool.

What You Bring

• 5+ years of experience with a heavy focus on backend systems — Python, Postgres, AWS.

• You've worked on real money movement. ACH origination and returns, RTP or FedNow, wires, or equivalent. You know what an R01 is, why NACHA return windows matter, and why a credit‑push rail changes the product flow and not just the API call.

• You've integrated more than one payment provider in production, and you've lived through one of them failing.

• You've handled large transactions, where the failure mode is a five‑ or six‑figure problem and someone notices immediately.

• You're API‑native. Webhooks, idempotency, eventual consistency, and exactly‑once delivery are your default vocabulary.

• Strong SQL and relational design. You know how to write a transaction that won't fail under load — including at auction close and during scheduled auto‑pay batches.

• Marketplace or two‑sided flow experience. Buyers and sellers, settlement between them, and the timing tension that creates.

• An obsession with reliability. You think deeply about idempotency, race conditions, and what happens on the third retry.

• Product‑owner thinking. You don't just build a pay button. You understand the flow of funds and how to communicate financial status clearly to a user who is worried about their money.

• Pragmatism. You know when to build a custom internal solution and when to leverage a third party to get the job done.

Strongly preferred: direct experience with Stripe, Plaid, Airwallex, PayPal, Modern Treasury, or Increase, and with evaluating or building a payment orchestration layer across more than one of them.

Strong plus: fraud, dispute, or chargeback work on a marketplace; hands‑on with risk tooling like Sardine, Sift, or Stripe Radar; enough React and TypeScript to ship the payment‑method and payout surfaces you own.

Bonus: distributed systems; stablecoin or on‑chain settlement; KYC/KYB, bank partnership, or bank‑sponsor program exposure; the alternative asset space. You collect, or you have a view on where this market is going.

How We’ll Interview You

We'll be specific so you can prepare. Before any of it: download the app, put a card up, make a bid, and try selling — go through the workflows. Every round assumes you've used the product, and we expect your point of view to sharpen as you go. For this role, look specifically at the deposit, payment method, and payout surfaces.

1. Recruiter screen — 25 minutes, Google Meet. Come ready to talk about the metric you own today and how you're performing against it, why Alt specifically, and how you're actually using AI. We'll answer your questions.

2. Hiring manager — 45 minutes, Google Meet. Be ready to go deep on the provider integration or money‑movement system closest to your own hands: what you built versus inherited, the trade‑offs you made, and what you'd change now.

3. Technical screen — 60 minutes. A hands‑on working session on a rail behaving badly — duplicate and out‑of‑order webhooks, a late return, a provider that acks and then times out — and a payout batch that has to complete exactly once. Think out loud.

4. Architecture and system design — 60 minutes. Design a payment orchestration layer under real constraints: two providers, failover mid‑batch, instant and batch payouts, a risk hold on a five‑figure transfer, and a ledger contract you don't control. We'll push back on at least one of your choices on purpose — how you take that matters as much as the design.

5. Culture interview — 30 minutes. How you work with the people who depend on your systems — operations, finance, support, and the customer on the other end of a held transfer.

6. Leore, our founder and CEO — 30 minutes. Everyone who joins Alt meets Leore. Come with a point of view on where you'd take Alt's money movement first.

7. Reference check(s) — 15 minutes with a former manager(s).

What we offer:

For full‑time Employees

• We cover 85% of your medical, dental, and vision, and up to 50% for dependents. HSA/FSA available

• Generous PTO that people actually take

• Parental leave at full salary

• $200/month wellness + $100/month home office stipend

• Free DoorDash Pass membership, because dinner shouldn't be a decision

• Remote‑first (for most positions), with WeWork access when you want a room with other humans

• 401(k)

• Alt Equity to all full‑time employees