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Senior Software Engineer, Add-Ons

Mozilla· Firefox
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Hybrid (Canada)CA$104k - CA$139kfull-timePosted 8mo ago

About the role

Senior Software Engineer role focused on building and evolving the Mozilla Add-ons platform (AMO), including DevHub, Reviewer tools, automated moderation pipelines, and related systems. Collaboration with engineers, reviewers, product support, and leadership to deliver features, improve reliability, and scale the Firefox add-ons ecosystem.

Responsibilities

  • 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 (Python/Django, MySQL, React/TypeScript, asynchronous processing); Internal developer platforms; Team process; Engineering standards; Platform reliability.

Qualifications

  • 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 (metrics, logging, tracing, SLOs, alerting).
  • Experience building or maintaining internal tools or platforms used by other engineering teams.
  • Experience defining or improving engineering practices (code review standards, operational readiness, runbooks, incident response, on-call, definitions of done).
  • Ability to read and understand unfamiliar codebases and trace behavior across frontend, backend, asynchronous jobs, data stores, and infrastructure.
  • Experience debugging complex production issues and turning learnings into lasting improvements.
  • Strong technical writing skills (design documents, ADRs, runbooks, incident reports).
  • Experience working iteratively with a visible backlog and stakeholder feedback leading to concrete improvements.
  • Strong collaboration and communication in distributed teams.
  • Willingness to mentor peers in operational and reliability practices.
  • Commitment to Mozilla values: welcoming differences, relationship-minded, responsible participation, grit.

Skills

Required:PythonDjangoReact/TypeScriptCI/CDObservabilityCode ReviewDocumentation
Nice to have:Infrastructure as Code

Benefits

  • Generous performance-based bonus plans
  • Rich medical, dental, and vision coverage
  • Generous retirement contributions with 100% immediate vesting
  • Quarterly all-company wellness days
  • Country-specific holidays plus a day off for your birthday
  • One-time home office stipend
  • Annual professional development budget
  • Quarterly well-being stipend
  • Paid parental leave
  • Employee referral bonus program
  • Other benefits (life/AD&D, disability, EAP, etc. - varies by country)
Last updated Sep 16, 2026. Interested? Apply on the company site.

About Mozilla

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Mozilla is the not-for-profit behind the lightning fast Firefox browser. We put people over profit to give everyone more power online.

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