Senior Software Engineer (Add-Ons)

Join Mozilla as a Senior Software Engineer, where you'll play a key role in enhancing the Firefox add-ons ecosystem. You'll work on major features and architectural improvements, establish engineering standards, create observability systems, and collaborate with various teams. This position offers a range of benefits, including health and wellness coverage, mental health support, generous time off, parental leave, financial incentives, learning and development opportunities, and more.

Experience with trust and safety, automated moderation, abuse prevention, or other adversarial systems

GBP 66,000 - 87,000

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, and improve our CI/CD pipelines using declarative, pipeline-as-code approaches.
• Strong understanding of observability as an engineering discipline, including metrics, logging, tracing, service-level objectives, and actionable alerting
• Experience working iteratively with a visible backlog, regular stakeholder feedback, and retrospectives that result in concrete improvements
• 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
• Ability to read and understand unfamiliar codebases and trace application behavior across frontend, backend, asynchronous jobs, data stores, and infrastructure
• Commitment to our values:

Requirements

• Strong collaboration and communication skills in a distributed team environment
• Experience operating and improving production software systems where reliability and safe delivery matter
• Experience designing or improving automated testing and deployment workflows, including integration testing and staged or progressive delivery
• Strong hands-on experience building and maintaining production applications with Python/Django
• Strong experience with CI/CD systems and treating pipelines and infrastructure declaratively as code
• A willingness to share knowledge and mentor peers in operational and reliability practices
• Strong technical writing skills, with experience creating useful documentation such as design documents, ADRs, runbooks, and incident reports
• Being relationship-minded
• Having grit
• Practicing responsible participation

Welcoming differences

• Experience defining or improving engineering practices such as code review standards, operational readiness, runbooks, incident response, on-call expectations, or definitions of done
• Experience debugging complex production issues and turning what you learn into lasting system improvements
• 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

Preferred

• Experience with chaos engineering, disaster recovery testing, or production readiness reviews
• Contributions to open source projects