Senior Software Engineer, Ledger

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 A collector borrows against a card they own. We size the advance, disburse it, hold the collateral, and manage the loan for however long it runs. Meanwhile an auction closes and hundreds of payouts go out at once, each against a different fee schedule — some by ACH, some by wire, some instant. Every one of those movements has to land in a double-entry ledger that still balances at the end of the day. That is the whole job. You own the ledger that is Alt's system of record, the money movement that feeds it, and the reconciliation that proves the two agree. 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 ledger where every cent is accounted for and every entry says who created it and when. In payments, "mostly working" is a failure. Financial correctness wants you to measure twice and cut once. The people who are great at this have owned a ledger somewhere it mattered, and they think in idempotency, race conditions, and reconciliation because they've been on the wrong side of all three. What You'll Own: The ledger as system of record. Entries, lines, balances, holds, reversals, and the states in between — pending, posted, available, canceled, declined, reversed. Immutability and audit trail as design constraints, not features. Point-in-time balances that let a customer see where they stood on any past date. You should be able to spot a modeling error in a schema review before it becomes a six-month cleanup, and explain why a balance is a derived value and not a column. 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. Payouts. Getting sellers and borrowers their money faster than anyone else in this market: instant payout options, batch payouts at auction close, and the settlement timing that makes them safe. Reconciliation. When the ledger and the processor disagree, you own the answer. Automated matching, an exception queue that a human can actually work, and breaks caught before a customer finds them. Lending infrastructure. Design and scale our lending products — credit disbursement through the automated lifecycle of loan management. Repayments, partial payments, advance reversals, state transitions, the loan that goes sideways. Provider architecture. Multi-PSP integrations built so the next one isn't a rewrite, and readiness for a single orchestration layer if that's where we land. Webhooks, idempotency, retry semantics, state machines, failure modes on the third retry. 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. Making it legible. The customer's account activity surface reads straight off your ledger: running balance, which method funded what, a full reconciliation of a single auction where someone both bought and sold. You'll ship some of that surface yourself, and you'll be the reason it's trustworthy. The trade-off calls. Shipping speed against uncompromising correctness; build custom versus buy. 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 your ledger against it Build an agent that triages the reconciliation exception queue overnight, clusters the breaks, and hands you a ranked list with a proposed cause for each instead of a wall of unmatched rows Put an MCP server over the ledger so "where did this discrepancy come from" is a question you ask in plain language rather than another one-off query against a table nobody else understands Use models to generate adversarial test cases for the lending and settlement state machines — the repayment that lands mid-default, the partial payment that arrives after a write-off, 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 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 worked with a double-entry ledger. Built one, migrated one, or owned one in production — and you can explain a modeling decision you'd make differently now. You've handled large transactions , where the failure mode is a five- or six-figure problem and someone notices immediately. Database mastery. Expert 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. You're API-native. Webhooks, idempotency, eventual consistency, and reconciliation are your default vocabulary. Marketplace or two-sided flow experience. Buyers and sellers, settlement between them, and the timing tension that creates. An obsession with correctness. You think deeply about idempotency, race conditions, and data consistency. 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. Strong plus: enough React and TypeScript to ship the customer-facing surface that reads off your ledger. This isn't a fullstack seat, but the person who can take a ledger change all the way to the UI will go further here. Bonus: distributed systems; credit or risk modeling; direct experience with Stripe, Plaid, Airwallex, PayPal, Modern Treasury, or Increase; evaluating or implementing a third‑party ledger service (Modern Treasury, Fragment, Formance, TigerBeetle or similar); stablecoin or on‑chain settlement; KYC/KYB, bank partnership, or SOX and audit‑readiness 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 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 cash advance, deposit, 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 with — 45 minutes, Google Meet. Be ready to go deep on the ledger 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 (Live Coder pad)
4. Architecture and system

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