Note: The job is a remote job and is open to candidates in USA. Alt is unlocking the value of alternative assets through a platform for buying, selling, vaulting, and financing trading cards. The Senior Software Engineer will own the company’s double-entry ledger, money movement, payment integrations, reconciliation, lending infrastructure, payouts, and related risk systems, with a focus on financial correctness and reliability.
Responsibilities
- 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
- 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
Skills
- 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
Benefits
- Equity for all full-time employees
- For full-time employees, 85% coverage of medical, dental, and vision, and up to 50% coverage for dependents
- HSA/FSA available
- Generous PTO that people actually take
- Parental leave at full salary
- $200/month wellness stipend
- $100/month home office stipend
- Free DoorDash Pass membership
- Remote-first for most positions, with WeWork access
- 401(k)
- Alt Equity to all full-time employees
Company Overview