Founding Engineer (Full Stack) ($150k-$225k + Equity) at Neptune

This is a job that Jill, our AI Recruiter, is recruiting for on behalf of one of our customers. She will pick the best candidates from Jack's network. The next step is to speak to Jack. Job Title Founding Engineer (Full Stack) Salary $150k-$225k + Equity Company Description Neptune is a $7.5M venture-backed startup building a shared AI brain for couples to manage major life decisions. Backed by Floodgate and The General Partnership, Neptune was founded by product and engineering leaders from Google, Stripe, and Uber to simplify complex financial and legal workflows through emotionally intelligent technology. Job Description As Neptune's first founding engineer, you will architect and build the core AI engine and product experience from the ground up. You'll work alongside world-class founders to turn emotionally charged financial decisions into seamless, trust-based workflows. This high-impact role involves setting the technical foundation while shipping features that directly influence how couples build wealth. Location New York, USA Why this role is remarkable Join a world-class founding team including the creator of Google Forms and the founding engineer of Stripe Link.Build a category-defining product backed by $7.5M from top-tier investors like Floodgate (early backers of Lyft, X, and Twitch).Gain massive ownership and founding-level equity while working with cutting-edge LLMs on high-trust, real-world financial and legal use cases. What You Will Do Design and ship the "Neptune brain," a shared context engine that manages a couple's full financial and legal history.Develop conversational AI and LLM-powered workflows that translate complex model outputs into high-credibility user experiences.Own features end-to-end across the stack, from backend architecture and Plaid integrations to frontend execution in Next.js. The ideal candidate Has 4–7 years of full-stack experience with a track record of shipping impactful production features in high-trust environments.Demonstrates deep "AI-native" intuition, using LLMs as force multipliers and understanding their performance across sensitive financial tasks.Possesses early-stage startup DNA, characterized by extreme agency, product-thinking, and the ability to thrive in an in-office NYC environment. Who are Jack & Jill? Ok, I'll go first. I'm Jack, an AI that gets to know you on a quick call, learning what you're great at and what you want from your career. Then I help you land your dream job by finding unmissable opportunities as they come up, supporting you with applications, interview prep, and moral support. And I'm Jill, an AI Recruiter who talks to companies to understand who they're looking to hire. Then I recruit from Jack's network, making an introduction when I spot an excellent candidate. How does this work? Jack's an AI agent for job searching and career coaching. He works for you.Jill is the AI recruiter working for the company. She recruits from Jack's network.If it's a match and the company wants to meet you, they'll make the intro. In the meantime, if you'd like, Jack will send you excellent alternatives. We never post fake jobs This isn't a trick. This is an open role that Jill is currently recruiting for from Jack's network. Sometimes Jill's clients ask her to anonymize their jobs when she advertises them, which means she can't share all the details in the job description. We appreciate this can make them look a bit suspect, but there isn't much we can do about it. Give Jack a spin! You could land this role. If not, most people find him incredibly helpful with their job search, and we're giving his services away for free.