Senior Software Engineer, -Ons

Why Mozilla?

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.

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 Dev Hub 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 Dev Hub.
• 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, Dev Hub and Reviewer tools modernization.
  • AMO application systems:
    Work within our Python/Django, MySQL, React/Type Script, 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…