Senior Software Engineer, Add-ons Platform & Reliability

Mozilla; Greater London; On-site; GBP 90,000 - 130,000; Full time

Benefits offered by this job

Health and dental

Mental health support

Paid leave

Retirement contribution

Professional development budget

Life/AD&D insurance

Wellbeing stipend

Remote work allowance

Job summary

Mozilla is seeking a Senior Software Engineer to advance the Firefox Add-ons ecosystem, delivering major features across the AMO stack and refining the DevHub and Reviewer tooling. You will help modernize the platform, improve architecture, and reach millions of users globally.

You will uphold engineering standards, build robust observability, and enhance CI/CD with pipeline-as-code. The role requires hands-on Python/Django, Kubernetes, and cloud experience, plus collaboration with product, QA,

Qualifications

• Strong hands-on experience building and maintaining production applications with Python/Django.
• Experience designing or improving automated testing and deployment workflows, including integration testing and staged or progressive delivery.
• Experience with Google Cloud and operating Kubernetes.

Responsibilities

• Deliver major features and architectural improvements across the Add-ons stack.
• 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 on 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, AMO application systems (Python/Django, MySQL, React/TypeScript), internal developer platforms, team process, engineering standards, platform reliability.

Skills

Python/Django

CI/CD

Observability

Documentation

Code reviews

Mentoring

Distributed team

Production debugging

Tools

Google Cloud

Kubernetes

Job description

Mozilla is seeking a Senior Software Engineer to advance the Firefox Add-ons ecosystem, delivering major features across the AMO stack and refining the DevHub and Reviewer tooling. You will help modernize the platform, improve architecture, and reach millions of users globally.

You will uphold engineering standards, build robust observability, and enhance CI/CD with pipeline-as-code. The role requires hands-on Python/Django, Kubernetes, and cloud experience, plus collaboration with product, QA,