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# Senior Fullstack Engineer, Payments

- **Company:** BSL - Applied Laser Technologies LLC
- **Location:** New York, NY, United States
- **Experience:** Expert
- **Salary:** $140,000.0 - $180,000.0
- **Contract:** Permanent contract
- **Skills:** Application Programming Interfaces (APIs), Amazon Web Services, Code Review, Databases, Relational Databases, Distributed Systems, Python (Programming Language), PostgreSQL, SQL Databases, Systems Integration, TypeScript, ReactJS, Backend, Front End Software Development
- **Published:** July 28, 2026
- **Apply:** https://www.manhattanjobs.com/job.asp?id=3333922100&tx=TT3734TYZ&pt=1&aff=0B19D771-A501-4A5E-8338-2A822B784D54&utm_source=Job%20Feed&utm_medium=textkernel&utm_campaign=DE&utm_term=0B19D771-A501-4A5E-8338-2A822B784D54

## About the Role

* 5+ years of experience with a heavy focus on backend systems (Python, Postgres, AWS) and a proven ability to build modern frontends (React, TypeScript).
 * Fintech or Payments experience: You've worked with ledgers, payment processors, or lending products and understand the complexities of moving money.
 * Database Mastery: You are an expert in SQL and relational database design-you know how to write a transaction that won't fail under load.
 * Fullstack Ownership: A track record of taking a complex financial feature from a technical design doc all the way to a polished UI in production.
 * Bonus: Experience with distributed systems, credit/risk modeling, or the alternative asset space.

## Description

We're looking for a Senior Fullstack Engineer who wants to build the financial engine of our platform. You're not just building a checkout flow; you're powering the liquidity that makes this marketplace work. You'll join a high-impact team responsible for our custom double-entry ledger, payment provider integrations, and our core lending products.

If you have a "measure twice, cut once" mindset for backend integrity but still move with a bias toward action on the frontend, you'll thrive here.

What You'll Do Here:

 * Engineer Financial Integrity: Build and maintain our custom-built double-entry ledger system to ensure every cent is accounted for across the platform.
 * Own Lending Infrastructure: Design and scale our lending products-from the logic of credit disbursements to the automated lifecycle of loan management.
 * Architect Integrations: Design and implement robust integrations with payment gateways and banking partners, ensuring 99.99% reliability and seamless reconciliation.
 * Own the UX of Money: Create high-trust user interfaces for payments and lending that make complex financial actions feel simple, transparent, and secure.
 * Balance Rigor with Speed: Make thoughtful trade-offs between rapid feature shipping and the uncompromising correctness required for financial systems.
 * Be a Multiplier: Level up the team through rigorous code reviews, technical documentation, and mentorship.

This is a perfect fit if youâ?¦

 * Are Obsessed with Correctness: You understand that in payments, "mostly working" is a failure. You think deeply about idempotency, race conditions, and data consistency.
 * Think Like a Product Owner: You don't just build a "pay button"; you understand the flow of funds and how to communicate financial status clearly to the user.
 * Love Building Infrastructure: You're energized by the challenge of building a ledger or a lending engine from the ground up.
 * Are Pragmatic: You know when to build a custom internal solution and when to leverage a third-party API to get the job done.


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