Senior Backend Engineer (Python/AWS) - Loan Servicing SaaS, Payments & Amortization (Ongoing)

THE ROLE Terra Notes is a bootstrapped B2B SaaS for private and seller-finance lenders: loan servicing, ACH payment collection, borrower management, subscription billing. We have live customers and real money moving every day. You'd be our second backend engineer, working alongside our existing lead and reporting to our Head of Product & Development. This is an ownership role, not ticket-taking: take a product goal, architect the right approach in our environment, and own delivery end to end, durably, the first time. THE STACK - Python on AWS serverless - Lambda functions via AWS SAM, Pipenv, pytest DynamoDB, Cognito (auth), API Gateway, SES, S3, Secrets Manager - Payments & verification: our ACH processor (ACH), Plaid (identity/verification), Authorize.net via Kurv (card) GitHub Actions CI/CD, Jira (SCRUM) WHAT YOU'LL OWN FIRST - Amortization engine hardening — fix payment-override re-amortization (loans must close to zero), payoff-as-of-any-date quoting, and effective-dated backdated payments with a full audit trail - Escrow module — ledger, escrow-first payment allocation, annual RESPA analysis engine, sweep routing - Advanced custom loans — step/variable rates, interest-only rollovers, per-diem payoff, custom schedule upload - General backend reliability on payment, billing, and verification flows WHAT WE'RE LOOKING FOR - 4+ years shipping production backend systems in Python - Real AWS serverless experience — Lambda, API Gateway, infrastructure-as-code (SAM). Please only apply if you've built and shipped serverless, not just monolithic web apps - Comfort with money-touching code: idempotency, reconciliation, dry-runs, staging verification before prod. You treat anything touching billing or all-customer data with extra care - Disciplined habits: testing, PR review, no cowboy deploys - Direct, honest communication — you flag problems early and you don't hide mistakes. This matters more to us than any single skill - Strong written English and reliable overlap with U.S. business hours NICE TO HAVE - Fintech, payments, or loan-servicing background, Plaid, or Authorize.net integration experience - Amortization / interest-calculation or accounting-systems experience HOW WE HIRE We start with a small paid trial project (real work, real pay) before any ongoing commitment. It's the fastest honest way for both sides to know if this is a fit. Details below. TO APPLY Send a short note (skip the generic template) covering: (1) a money-touching or data-critical backend system you've shipped and how you made sure it was correct, (2) your AWS serverless and any payments/fintech experience (3) a time you caught or surfaced a serious bug before it caused damage, and what you did.