Principal Engineer

Summary

Join Mozilla's New Products team as a founding Principal Software Engineer to build a browser-automation stack for AI agents. Define and communicate the long-term technical roadmap, write high-performance code in Go, Ruby on Rails, and TypeScript, and design distributed, fault-tolerant services. Lead and mentor a team of engineers, collaborate with product, design, and developer-relations teams, and communicate technical trade-offs to various stakeholders. This role requires 10+ years of software engineering experience, expert-level proficiency in at least two specified languages, and a proven track record of architecting and shipping complex systems. A deep understanding of browser internals, automation frameworks, and secure web interaction paradigms is essential. The position offers generous performance-based bonuses, rich medical, dental, and vision coverage, generous retirement contributions, wellness days, country-specific holidays, a home-office stipend, and more.

Requirements

• 10+ years of software engineering experience building high-performance developer tools, SDKs, or distributed systems, with at least 3 years leading technical teams or large projects
• Expert-level proficiency in at least two of: Go, Ruby (Rails), Python or TypeScript/JavaScript
• Proven track record architecting and shipping complex, high-throughput systems in production environments (cloud, edge, or hybrid)
• Deep understanding of browser internals, automation frameworks (e.g., Playwright, Puppeteer, Selenium), and secure web interaction paradigms
• Hands-on experience and opinions about modern AI/ML workflows or agent frameworks such as LangChain, LlamaIndex, or custom in-house systems
• Strong focus on code quality, testability, performance, and operational excellence; familiarity with TDD, automated testing, and observability stacks
• Exceptional communication skills with the ability to collaborate across disciplines and levels, from junior engineers to executive leadership

Responsibilities

• Technical Strategy & Architecture: Define and communicate the long-term technical roadmap for our browser-automation stack, balancing rapid iteration with long-term maintainability and scalability
• Hands-On Development: Write elegant, high-performance code daily in languages such as Go, Ruby on Rails, and TypeScript. Rapidly prototype, benchmark, and ship features to production
• System Design & Infrastructure: Design distributed, fault-tolerant services and developer-facing SDKs/APIs. Own cloud infrastructure, CI/CD pipelines, security, and observability
• Team Leadership & Mentorship: Grow, mentor, and inspire a world-class engineering team. Conduct thoughtful code reviews, establish the engineering culture, and foster a team of technical excellence and psychological safety
• Collaboration & Product Direction: Work closely with product, design, and developer-relations to ensure technical choices align with developer needs and business goals. Turn community feedback into concrete improvements
• Stakeholder Communication: Translate complex technical trade-offs into clear language for executives, partners, and cross-functional teams. Provide regular updates on progress, risks, and mitigation strategies

Preferred Qualifications

• Prior experience as a founding or early-stage CTO, Principal Engineer, or Staff+ engineer at a fast-growing startup or open-source project
• Experience building to production systems in browser automation, AI tooling, or developer infrastructure
• Knowledge of privacy-preserving technologies, secure computation, or web standards bodies
• Experience optimizing build systems, WebAssembly pipelines, or cross-language bindings
• Public speaking or writing history (talks, blogs, whitepapers) explaining complex technical topics to diverse audiences

Benefits

• Generous performance-based bonus plans to all eligible employees – we share in our success as one team
• Rich medical, dental, and vision coverage
• Generous retirement contributions with 100% immediate vesting (regardless of whether you contribute)
• Quarterly all-company wellness days where everyone takes a pause together
• Country-specific holidays plus a day off for your birthday
• One-time home-office stipend
• Annual professional development budget
• Quarterly well-being stipend
• Considerable paid parental leave
• Employee referral bonus program
• Other benefits (life/AD&D, disability, EAP, etc. – varies by country)