Staff Full Stack Software Engineer - Core Products

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 over 500,000 small business owners nationwide can focus on their craft and their employees. AI is a fundamental part of how work gets done at Gusto, and all team members actively engage with AI tools to accelerate development workflows, improve testing frameworks, and scale engineering safety across teams.

As a Staff Full Stack Software Engineer, you will operate across the full product lifecycle for Gusto’s core customer-facing platforms (Payroll, Benefits, HR, Gusto Money, Gusto Solo, Gusto Pro). You will architect and scale one of the largest Ruby on Rails and JavaScript/React monolithic applications in the world. Operating as a senior technical leader, you will own multi-quarter engineering projects, execute large-scale refactors, optimize system performance, leverage emerging AI frameworks, and mentor engineers across the organization.

Key Responsibilities

• Core Product Architecture: Design, build, test, and maintain features across Gusto's core product suite, including Payroll, Health Benefits, HR, Retirement, Gusto Money, and Gusto Pro.
• Large-Scale Platform Evolution: Help scale, refactor, and maintain one of the world's largest production Ruby on Rails and JavaScript/React codebases for high availability and low latency.
• AI-Accelerated Engineering: Leverage state-of-the-art AI tools and agentic frameworks to accelerate feature development, enhance test coverage, optimize system refactoring, and share best practices across engineering pods.
• Multi-Quarter Technical Leadership: Own ambiguous, multi-quarter technical initiatives from initial concept through technical spec, rollout, and long-term monitoring, solving complex scalability challenges.
• Cross-Functional Collaboration: Partner directly with Product Management, Data Science, Design, and Platform Engineering teams to prototype, iterate, and ship high-impact features daily.
• Mentorship & Technical Guidance: Mentor engineers across teams to solve complex technical problems, raise engineering quality standards, and maximize career development.

Requirements

Technical Craft & Staff Engineering Depth

• 10+ years of professional software engineering experience with deep full-stack architecture depth.
• Large-Scale Full-Stack Mastery: Demonstrated experience building and operating high-throughput web applications using modern backend technologies (Ruby on Rails preferred, Python/Django, Node.js) and frontend ecosystems (React, TypeScript).
• Codebase Scaling & Refactoring: Proven track record leading large-scale architectural refactors, resolving performance bottlenecks, and maintaining high reliability across complex domain models.
• AI Tooling & Automation Fluency: Hands-on experience applying emerging AI tools or frameworks to streamline software development, refine testing suites, or deliver AI-powered product capabilities.
• System Ownership & Impact: Track record of owning multi-quarter engineering roadmaps that solve hard infrastructure/business challenges and deliver measurable customer value.
• Technical Mentorship: Demonstrated ability to mentor and elevate junior and senior engineers, driving technical excellence across teams.

Preferred Qualifications

• Deep domain expertise in fintech, payroll processing, benefits administration, tax compliance, or HR tech.
• Hands-on experience scaling large monolithic architectures into domain-oriented modular services.
• Experience experimenting with and safely deploying generative AI frameworks in enterprise production environments.

Total Rewards & Benefits

• Compensation & Equity: Tiered base salary ($163,000 – $247,000 USD) + Restricted Stock Units (RSUs) grants so every employee shares in company success.
• Healthcare & Wellness: Comprehensive medical, dental, and vision insurance options for employees and eligible dependents.
• Time Off & Rest: Flexible time off policy, paid company holidays, sick leave, and paid parental leave.
• Growth & AI Tools: Dedicated learning stipends, continuous AI skill-building resources, and modern technical tooling.