Senior Software Engineer

About the role

SENIOR SOFTWARE ENGINEER (FULL-STACK, AI-NATIVE)

Marvin · Denver/Los Angeles - Hybrid 2-day in office · Full-time · $160k-190k

ABOUT MARVIN

Marvin helps people navigate their mental health and wellbeing. We partner with employers and health plans to give their members one place to understand their coverage, find care, and get support, including an AI coach built into the product. We're a small team shipping a production healthcare application, which means every engineer touches things that matter and owns them end to end.

THE ROLE

We're hiring a senior full-stack engineer who has made AI a core part of how they build software, not a novelty. This is not a machine learning research role. You won't train models or tune GPUs. You will ship product in a modern TypeScript/Next.js stack, and you'll do it with AI woven into both the product and your own workflow.

Two things distinguish this role from a standard senior web position:

1. You build with AI. You've moved well past autocomplete. You direct agentic coding tools to do real, multi-step work, you know exactly where they break, and you own every line they produce.

2. You build AI into the product. You've shipped LLM-backed features to real users and lived with them in production: prompts, tool calls, evals, tracing, cost, latency, and failure modes.

WHAT YOU'LL DO

- Own features end to end across our Next.js/React/TypeScript app, Prisma/Postgres backend, and AWS infrastructure.

- Extend our AI coach and build new LLM-powered member experiences: retrieval over benefits data, structured extraction, guided flows, and agentic tool use against our own APIs.

- Design evaluation and observability for AI features so we know when they get worse, not just when they crash.

- Push our AI-assisted development practice forward: agent instructions, reusable skills, hooks, MCP integrations, and review practices that keep quality high as velocity climbs.

- Handle sensitive health data responsibly. PHI boundaries, redaction, audit trails, and vendor data agreements are part of the design, not an afterthought.

- Review code, whether written by a human or an agent, with a critical eye. Mentor teammates and raise the bar on testing and reliability.

WHAT WE'RE LOOKING FOR

Core engineering

- 5+ years building production web applications, with deep TypeScript, React, and Node experience. Next.js is a strong plus.

- Comfort across the stack: relational data modeling (we use Prisma and Postgres), auth flows, caching, background jobs, and cloud deployment (AWS, Docker, Terraform or similar).

- A real testing habit at every layer: unit, component, and end-to-end. We use Vitest, Storybook, Cypress, and Playwright.

- Strong product judgment and the ability to work directly with design, clinical, and partner-facing teammates.

AI fluency (the part that sets you apart)