Senior Software Engineer, Add-Ons
Thunderbird
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Job summary
Mozilla Corporation is seeking a Senior Software Engineer for the Add-Ons stack within the Firefox ecosystem. The role focuses on delivering major features, improving reliability, and enhancing tooling for reviewers, DevHub, and automated moderation.
You will work across Python/Django backends, MySQL data stores, and React/TypeScript frontends in a distributed, remote-friendly setup.
Qualifications
- Strong experience building production apps with Python/Django.
- Proven ability to operate and improve reliable production software.
Responsibilities
- Deliver major features and architectural improvements across the Add-ons stack.
- Establish and maintain engineering standards including code review and production readiness.
- Create robust observability systems and data-backed insights.
- Provide peer feedback and mentor peers in reliability practices.
- Improve CI/CD pipelines with declarative, pipeline-as-code approaches.
- Write clear technical documentation such as design notes and ADRs.
Skills
Tools
Job description
at Mozilla Corporation
Team: Firefox
Locations: Remote Netherlands, Remote UK, Remote France, Remote Canada, Remote Germany, Remote Finland, Remote Belgium, Remote Spain, Remote Sweden
Mozilla Corporation is the non-profit-backed technology company that has shaped the internet for the better over the last 25 years. We make pioneering brands like Firefox, the privacy-minded web browser. Now, with more than 225 million people around the world using our products each month, we’re shaping the next 25 years of technology and helping to reclaim an internet built for people, not companies. Our work focuses on diverse areas including AI, social media, security and more. And we’re doing this while never losing our focus on our core mission - to make the internet better for people. The Mozilla Corporation is wholly owned by the non-profit 501(c) Mozilla Foundation. This means we aren’t beholden to any shareholders — only to our mission. Along with thousands of volunteer contributors and collaborators all over the world, Mozillians design, build and distribute open-source software that enables people to enjoy the internet on their terms.
addons.mozilla.org (AMO) is the foundation of the Firefox add-ons ecosystem. It’s a showcase for developers to publish and grow their extensions, and a place of discovery for millions of users who customize Firefox to make it their own. Behind the scenes are the DevHub which enables developers to manage their extensions. To manage the ecosystem there are a series of Reviewer tools and automated moderation systems.
- Deliver major features and architectural improvements across the Add-ons stack, including automated moderation pipelines, Reviewer tools, and DevHub.
- Help establish and maintain engineering standards across areas such as code review, definition of done, production readiness, runbooks, incident response, on-call practices, coding conventions, and infrastructure as code.
- Create robust observability systems and data-backed insights.
- Provide peer feedback, share knowledge and help others grow.
- Build and improve the systems that enable Add-ons engineering to safely develop, deploy, observe, and operate production services.
- Improve our CI/CD pipelines using declarative, pipeline-as-code approaches that make changes reproducible, testable, and easy to review.
- Deliver work iteratively using a visible backlog, short feedback cycles, retrospectives, and demonstrations to stakeholders.
- Write clear technical documentation, including design notes, Architecture Decision Records, runbooks, and incident write-ups.
- Work effectively in unfamiliar codebases, tracing requests and asynchronous jobs end-to-end to understand failures and identify opportunities for improvement.
- Collaborate with designers, product managers, QA, and community contributors to deliver end-to-end improvements.
- Contribute in the open through pull requests, code reviews, and discussions.
- Work on:
- Feature development: submission flows, trust and safety signals, DevHub and Reviewer tools modernization.
- AMO application systems: Work within our Python/Django, MySQL, React/TypeScript, and asynchronous processing systems.
- Internal developer platforms: Create tools and paved paths that make it easier for teams to ship and operate software safely and consistently.
- Team Process: Contribute to team ceremonies, execute process improvement, and provide feedback on team effectiveness.
- Engineering standards: Help make production readiness, testing, recoverability, documentation, and safe deployment part of the normal development lifecycle.
- Platform reliability: Deployments, monitoring, and incident response.
- Strong hands-on experience building and maintaining production applications with Python/Django.
- Experience operating and improving production software systems where reliability and safe delivery matter.
- Strong experience with CI/CD systems and treating pipelines and infrastructure declaratively as code.
- Experience designing or improving automated testing and deployment workflows, including integration testing and staged or progressive delivery.
- Strong understanding of observability as an engineering discipline, including metrics, logging, tracing, service-level objectives, and actionable alerting.
- Experience building or maintaining internal tools or platforms used by other engineering teams, with an understanding that internal systems have users, reliability expectations, roadmaps, and lifecycle considerations.
- Experience defining or improving engineering practices such as code review standards, operational readiness, runbooks, incident response, on-call expectations, or definitions of done.
- Ability to read and understand unfamiliar codebases and trace application behavior across frontend, backend, asynchronous jobs, data stores, and infrastructure.
- Experience debugging complex production issues and turning what you learn into lasting system improvements.
- Strong technical writing skills, with experience creating useful documentation such as design documents, ADRs, runbooks, and incident reports.
- Experience working iteratively with a visible backlog, regular stakeholder feedback, and retrospectives that result in concrete improvements.
- Strong collaboration and communication skills in a distributed team environment.
- A willingness to share knowledge and mentor peers in operational and reliability practices.
- Commitment to our values:
- Welcoming differences
- Being relationship-minded
- Practicing responsible participation
- Having grit
- Experience with Google Cloud and operating Kubernetes.
- Experience with infrastructure-as-code tooling and policy-as-code.
- Experience establishing SLOs and error-budget-based reliability practices.
- Experience with chaos engineering, disaster recovery testing, or production readiness reviews.
- Experience with trust and safety, automated moderation, abuse prevention, or other adversarial systems.
- Contributions to open source projects
- 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)
Mozilla exists to build the Internet as a public resource accessible to all because we believe that open and free is better than closed and controlled. When you work at Mozilla, you give yourself a chance to make a difference in the lives of Web users everywhere. And you give us a chance to make a difference in your life every single day. Join us to work on the Web as the platform and help create more opportunity and innovation for everyone online.
Mozilla understands that valuing diverse creative practices and forms of knowledge are crucial to and enrich the company’s core mission. We encourage applications from everyone, including members of all equity-seeking communities, such as (but certainly not limited to) women, racialized and Indigenous persons, persons with disabilities, persons of all sexual orientations, gender identities, and expressions.
We will ensure that qualified individuals with disabilities are provided reasonable accommodations to participate in the job application or interview process, to perform essential job functions, and to receive other benefits and privileges of employment, as appropriate. Please contact us at hiringaccommodation@mozilla.com to request accommodation.
We are an equal opportunity employer. We do not discriminate on the basis of race (including hairstyle and texture), religion (including religious grooming and dress practices), gender, gender identity, gender expression, color, national origin, pregnancy, ancestry, domestic partner status, disability, sexual orientation, age, genetic predisposition, medical condition, marital status, citizenship status, military or veteran status, or any other basis covered by applicable laws. Mozilla will not tolerate discrimination or harassment based on any of these characteristics or any other unlawful behavior, conduct, or purpose.
Remote Finland
€45.000-€60.000 EUR
- Remote Netherlands
- Remote UK
- Remote France
- Remote Canada
- Remote Germany
- Remote Finland
- Remote Belgium
- Remote Spain
- Remote Sweden
At Mozilla, we’re serving humanity—by maintaining a safe, open internet—while also helping the individual humans employed here to reach their personal and professional goals. With a relatively small team serving hundreds of millions of people, a culture of exploration, and a commitment to mentorship, opportunities abound to learn and grow at Mozilla.
- Purpose is built into our work, with our mission driving every decision
- We challenge assumptions, the status quo, ourselves, and each other
- We are transparent: in our code, our business partnerships, and our everyday interactions
- We seek out people from diverse backgrounds and with perspectives different from our own
- We pair purpose with performance and put people ahead of profit
- 1000+ paid staff from over 30 countries
- Thousands of volunteer contributors across six continents
- 2 global offices: Berlin and Toronto
- 9 coworking space locations: San Francisco, San Mateo, London, Paris, Portland, Tulsa, Vancouver, Chicago, and Bellevue
- Hundreds of home offices globally
- Flexible work environment (majority of Mozillians work remotely)
- Industry-leading paid parental leave (up to 26 weeks of fully paid leave for childbearing parents and up to 12 weeks for non-childbearing parents)
- Reimbursement for professional development (up to $3,000/year)
- A work setup including the latest hardware and software of your choice
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