Frontend Full Stack Software Engineer, AI Platform

About Gusto

At Gusto, we're on a mission to grow the small business economy. We handle the hard stuff — payroll, health insurance, 401(k) s, and HR — so owners can focus on their craft and their customers. With teams in Denver, San Francisco, and New York, we support more than 500,000 small businesses nationwide and are building a workplace that reflects the people we serve.

All full-time employees receive competitive base pay, benefits, and equity (RSUs) — because everyone who helps build Gusto should share in its success. Offer amounts are determined by role, level, and location. Learn more about our Total Rewards philosophy.

AI is a fundamental part of how work gets done  expect all team members to actively engage with AI tools relevant to their role and grow their fluency as the technology evolves. AI experience requirements vary by role and will be assessed during the interview process.

San Francisco Bay Area, New York City Metro, or Seattle Metro.

We're hiring an experienced full stack engineer to help small businesses work better with AI. You'll build Gus, Gusto's AI-powered assistant, and create scalable solutions that serve millions of users. As a Software Engineer at this level, you'll own projects end-to-end from initial specs to deployed features—working at the intersection of modern AI capabilities and real business needs.

The Core Experience - AI Experiences team owns Gus, Gusto's AI-powered assistant, and the platform that enables teams across Gusto to deliver AI-native experiences to customers across web, mobile, voice, email, and agent-based channels. You'll work with in Gusto's AI platform infrastructure, collaborating closely with sister teams who own the underlying agent framework. Your focus is building experiences and enabling product teams to extend and scale within the platform.

This work is directly tied to Gusto's top priorities. We operate with fast iteration cycles, deep cross‑functional collaboration, and high ownership.

• Architect, build, and test technologies supporting AI experiences within Gusto's product suite
• Create standardized, self‑serve patterns that enable product teams to extend Gus across web, voice, email, and agent‑based experiences
• Collaborate with ML and product teams on prompt engineering, clarifying question flows, and escalation logic—using A/B tests and data to drive improvements
• Mentor engineers on complex technical challenges in AI, scalability, and platform infrastructure
• Help scale a large Ruby/Rails and React application serving millions of users
• Work with Product, Design, Security, and Technical Operations teams to understand customer needs, develop solutions, and launch features
• Build customer‑facing products end‑to‑end that customers rely on every day

• 8+ years of software development experience, with 4+ years building scalable platforms or high‑impact customer‑facing products
• Strong foundation in front‑end engineering and modern web technologies (Ruby on Rails, React, GraphQL, or similar full‑stack frameworks) with ability to build well‑structured, maintainable code
• Track record of owning multi‑quarter projects that solve complex engineering problems and deliver measurable customer impact at scale
• Experience building internal platforms or developer‑facing infrastructure that enables other teams to self‑serve and ship AI‑powered features
• Excellent cross‑functional communication skills with ability to mentor engineers and collaborate effectively across teams and stakeholders
• Product‑minded, customer‑facing engineering approach with passion for creating great customer experiences and ownership over performance, reliability, and quality
• Bonus if you have AI platform development experience or strong learning orientation toward AI technologies, patterns, and frameworks (orchestration, evals, prompt systems—not ML model development)

Our cash compensation amount for this role is targeted at $163,000-$204,000 in Denver, $178,000-$223,000 for Los Angeles and most remote locations, $197,000-$247,000 for San Francisco, New York, and Seattle. Final offer amounts are…