Backend Engineer, Underwriting

Pylon; San Francisco (CA); On-site; USD 140,000 - 220,000; Full time

Benefits offered by this job

Equity

Benefits

Job summary

Pylon, a Palo Alto-based fintech company, is hiring Back End Engineers for our underwriting team. You will encode mortgage rules into software, collaborating with mortgage experts to translate guidelines into precise logic and robust, scalable systems.

Join a fast-moving team applying AI to mortgage origination, using modern stacks like TypeScript, NestJS, GraphQL, and PostgreSQL. On-site in Palo Alto, CA with strong equity and benefits.

Qualifications

• Experience encoding mortgage rules into software with DSLs.
• Ability to work with domain experts to translate guidelines into logic.
• Strong emphasis on test coverage, correctness, and scalable systems.

Responsibilities

• Encode natural language mortgage rules into code using DSLs.
• Collaborate with mortgage experts to understand rules and exceptions.
• Build precise, robust systems with thorough testing and clear failure modes.
• Apply AI techniques to enhance underwriting processes.
• Automate regulated, high-stakes workflows to speed decisions.

Skills

TypeScript

Rule encoding

AI/ML tooling

NestJS

GraphQL

SQL PostgreSQL

Temporal.io

Tools

Custom DSLs

NestJS

GraphQL

Job description

About Pylon

America’s $13T mortgage market is one of the most important financial systems in the world. It underwrites the middle class and is the mechanism through which millions of families build wealth. But while every other financial instrument has been simplified to an API call, mortgages are still assembled by hand.

We started from zero and created the first vertically integrated mortgage platform that turns origination into a single API.

Publicly traded companies and the country’s largest originators are already building on Pylon. Revenue is compounding monthly. We’re backed by Peter Thiel, Conversion Capital, QED, Citi, Fifth Wall, and the founders of Ramp, Blend, and Mercury.

Working at Pylon isn’t for those seeking comfort. The people who thrive here have high agency, strong opinions, and a track record of delivering outcomes without direction. Many of us are former founders. We move quickly, challenge each other directly, and take full ownership of results. It’s hard work, but it will be worth it.

Join us in building America’s mortgage rails.

The Team

We’re looking for Back End Engineers to join our Underwriting team. This is the team that takes human judgment out of mortgage origination — and replaces it with systems that are faster, more consistent, and more accurate than any human process could be.

Mortgage underwriting today is mostly manual. Experts read guidelines, interpret rules, cross-reference documents, and make decisions that determine whether someone gets a home. We’re encoding all of that into software. Nobody has fully cracked this yet. The companies that figure it out will define the next generation of lending.

The stakes are real. An incorrectly modeled rule can cost the company tens of thousands of dollars on a single loan. A well-modeled system can help us outcompete everyone in the market.

Here Is What You’ll Do

• Encode natural language rules into code. You’ll work with DSLs and novel techniques — including AI — to translate dense regulatory guidelines into executable logic. Think of it as compiling English into a system that makes six-figure decisions.

• Work side‑by‑side with mortgage experts. You won’t be guessing what the rules mean. You’ll pair with people who’ve spent their careers in mortgage to understand nuance, exceptions, and the “it depends” that makes this domain so hard.

• Build systems where correctness is everything. This isn’t a domain where “close enough” works. You’ll design for precision, build robust test coverage, and think deeply about failure modes.

• Push into uncharted territory. We’re applying AI in ways the mortgage industry hasn’t seen. You’ll help define what’s possible — not just implement what’s been done before.

• Automate complex, regulated processes. Every rule you encode is a step toward a world where mortgages are faster, cheaper, and more accessible.

Tech Stack

• TypeScript

• Custom DSLs for rule encoding

• AI/ML tooling and agentic infrastructure

• NestJS + GraphQL

• SQL (PostgreSQL)

• Temporal.io (workflow orchestration)

Who Will Succeed Here

Someone who:

• Is deeply curious

• Wants to own features from design to development to deployment to maintenance

• Is willing to put the work in to solve the hardest of problems

Location: Palo Alto , CA Base Salary Range: $140,000/yr to $220,000/yr + Equity + Benefits