Software Engineer (Senior)

Pax; San Francisco (CA); On-site; USD 180,000 - 240,000; Full time

Job summary

Pax in San Francisco is seeking a senior software engineer to own major product areas end to end, from problem framing to deployment. You will design durable APIs, data models, and AI-powered workflows, build across the stack, and collaborate with enterprise customers to translate needs into reliable software.

This role emphasizes mentorship, architecture, and long-term maintainability. Ideal candidates blend backend and frontend expertise with a passion for learning difficult domains and

Qualifications

• Proven track record shipping production software at scale.
• Deep backend and frontend capabilities.
• Experience with large language models is a plus.
• Ability to learn difficult domains quickly.

Responsibilities

• Own major product areas end to end.
• Design APIs, data models, workflows for high-stakes data.
• Build across the stack: backend, data pipelines, AI workflows, interfaces.
• Translate complex regulations and trade data into reliable products.
• Collaborate with enterprise customers to ship solutions quickly.
• Set technical direction with a focus on speed, quality, maintainability.
• Mentor other engineers and contribute to engineering culture.
• Shape technical roadmap and architecture for scalable systems.
• Leverage LLMs where they create leverage and ensure determinism where needed.

Skills

Software engineering

Mentorship

Communication

Ambiguity handling

Tools

React

Next.js

FastAPI

SQLModel

PostgreSQL

Job description

Our Mission

Global trade is one of the hardest, highest-stakes industries in the world and the software that runs it has never kept up.

Pax is changing that.

Pax is the AI control tower for global trade. Enterprises like Verkada, Glossier, Yamaha, and Kodak use Pax as the intelligence layer for their trade-compliance operations: connecting fragmented data, continuously auditing transactions, preparing and filing claims, and recovering money that has quietly slipped away for years.

We started with duty drawback, a $10B-per-year opportunity hiding in plain sight. Now, we’re building the operating system for how enterprises manage trade compliance and recover every dollar they’re owed.

Our platform includes:

• Duty drawback: Recover tariffs paid on goods that are later exported, returned, or destroyed. (Live.)
• IEEPA and reciprocal tariff recovery: Claim refunds associated with the latest wave of tariffs. (Live.)
• Entry and export audits: An AI agent that reviews customs transactions line by line and catches errors before they reach U.S. Customs and Border Protection. (Shipping now and you could own a meaningful part of it.)

This is only the beginning. Our goal is to build the complete control tower for global trade.

Tariffs have become a board-level concern. Companies have faced rates ranging from 25% to 145%, creating an urgent need for software that can turn complex regulations and fragmented records into accurate, actionable decisions. There has never been a better time to make a tangible impact on real businesses.

Who’s building this

Pax was founded by people who lived this problem.

Penny Chen, our CEO, holds a PhD from MIT and previously built optimization systems at Flexport and for Amazon’s last-mile supply chain. Chris Le is a repeat founder who previously worked at Brex, TikTok, and Amazon, including on last-mile supply-chain optimization.

We started Pax after seeing billions of dollars in refunds go unclaimed while working alongside the importers entitled to them.

We’re well-capitalized, serve real enterprise customers, and are looking for a senior software engineer to take ownership of critical products and systems. This is an opportunity to join early enough to shape the company, its engineering culture, and the future of a $10B-plus industry.

What you’ll do

• Own major product areas end to end, from customer problem and technical design through implementation, launch, and iteration
• Design durable APIs, data models, workflows, and system boundaries for products operating on high-stakes financial and regulatory data
• Build across the stack, including backend systems, data pipelines, AI-powered workflows, and polished customer-facing interfaces
• Turn complex regulations and messy trade data into products that feel simple and reliable
• Work directly with enterprise customers to understand their operations, identify the real problem, and ship solutions quickly
• Establish technical direction while making pragmatic decisions about speed, quality, and long-term maintainability
• Raise the engineering bar through thoughtful design, strong execution, clear communication, and mentorship
• Help shape our engineering culture, architecture, hiring, and technical roadmap
• Build with large language models where they create real leverage and use deterministic systems where accuracy demands them

What your first 90 days could look like

• Week 1: Ship a meaningful improvement to production and develop a working understanding of our product, customers, and trade-compliance domain.
• First 30 days: Own and deliver an end-to-end project alongside a founder, likely involving AI-assisted workflows, complex data, or regulatory logic.
• By 60 days: Take responsibility for a major product or technical area, including its architecture, execution plan, and production quality.
• By 90 days: Work directly with enterprise customers, turn ambiguous operational problems into product decisions, and lead delivery from discovery through adoption.

You might build systems that reconcile tens of millions of dollars in annual trade volume, interpret thousands of pages of federal regulations, transform customs documents into structured data, or help an AI agent audit every line of an import entry before it reaches the government.

The ideal candidate

• Has a strong record of building and shipping meaningful software at a high-growth startup or other demanding technical environment
• Has led substantial projects from an ambiguous problem through architecture, implementation, launch, and iteration
• Can go deep on backend architecture while caring deeply about product quality and a crisp user experience
• Writes reliable systems for complex, high-stakes workflows and knows where additional safeguards are necessary
• Is excited to build with large language models, understands their limitations, and thinks carefully about evaluation, reliability, and human oversight
• Makes sound tradeoffs between speed, simplicity, and scalability
• Communicates clearly with technical teammates, founders, customers, and domain experts
• Is comfortable operating with ambiguity and creating structure where none exists
• Acts without waiting for permission while knowing when a decision needs broader input
• Wants to own business and customer outcomes, not just code
• Helps other engineers do their best work through mentorship, feedback, and strong technical judgment
• Has substantial experience with technologies such as React, Next.js, FastAPI, SQLModel, PostgreSQL, or comparable frameworks

Experience in global trade or customs compliance is not required. We care more about your ability to learn difficult domains, make good decisions, and build exceptional software.

Why Pax

We’re a small team by design. You’ll have direct access to customers, meaningful influence over company direction, and ownership that would take years to earn at a larger organization.

The problems are technically demanding, operationally important, and tied directly to customer value. Your work will help enterprises navigate global trade, remain compliant, and recover millions of dollars they would otherwise lose.

This is early enough for your work to shape both the future of Pax and the industry we’re transforming. We believe it can be the most fulfilling work of your career.

Location and immigration

We work together in person in San Francisco. Our office is focused, fast-moving, and full of energy. This is a hard requirement; the role is not remote.

For immigration support, we can accommodate TN visas and eligible visa transfers. Due to timing constraints, we cannot sponsor new H-1B petitions.