> Markdown version of [/jobs/ext/4008049-senior-software-engineer-add-ons](https://www.wearedevelopers.com/jobs/ext/4008049-senior-software-engineer-add-ons). Every page supports `.md` or `Accept: text/markdown`. Links point to the HTML versions so they work for humans too. Agent guide: [/agents.md](https://www.wearedevelopers.com/agents.md). --- # Senior Software Engineer (Add-Ons) - **Company:** Mozilla - **Location:** Paris, France (Remote available) - **Experience:** Expert - **Contract:** Permanent contract - **Skills:** Automation of Tests, Code Review, Continuous Integration, Data Stores, Software Debugging, Software Design Documents, Django Web Framework, Data Intelligence, Python (Programming Language), MySQL, Reliability Engineering, Runbook, TypeScript, Policy as Code, Data Logging, Google Cloud, ReactJS, System Availability, Delivery Pipeline, Backend, Integration Tests, Kubernetes, Free and Open-Source Software, Front End Software Development - **Published:** October 29, 2026 - **Apply:** https://www.welcometothejungle.com/en/companies/mozilla/jobs/senior-software-engineer-add-ons_paris_pswpfp7c ## About the Role * Strong understanding of observability as an engineering discipline, including metrics, logging, tracing, service-level objectives, and actionable alerting * Experience designing or improving automated testing and deployment workflows, including integration testing and staged or progressive delivery * Experience working iteratively with a visible backlog, regular stakeholder feedback, and retrospectives that result in concrete improvements * Being relationship-minded * Having grit * Experience operating and improving production software systems where reliability and safe delivery matter * Strong hands-on experience building and maintaining production applications with Python/Django * Practicing responsible participation * A willingness to share knowledge and mentor peers in operational and reliability practices * 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 * Commitment to our values: * Strong collaboration and communication skills in a distributed team environment * Ability to read and understand unfamiliar codebases and trace application behavior across frontend, backend, asynchronous jobs, data stores, and infrastructure * Welcoming differences * 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 * Strong technical writing skills, with experience creating useful documentation such as design documents, ADRs, runbooks, and incident reports * Strong experience with CI/CD systems and treating pipelines and infrastructure declaratively as code * Experience with Google Cloud and operating Kubernetes * Experience with infrastructure-as-code tooling and policy-as-code * Experience with chaos engineering, disaster recovery testing, or production readiness reviews * Experience establishing SLOs and error-budget-based reliability practices * Experience with trust and safety, automated moderation, abuse prevention, or other adversarial systems * Contributions to open source projects ## Description * As a Senior Software Engineer, you'll bring a passion for crafting resilient systems that accelerate our review and moderation teams to provide a first-class experience for Add-on developers. You'll work closely with engineers, reviewers, developer support, and Add-ons leadership to turn ideas into polished features, modernize the platform and its architecture, and see your work reach millions of people around the world * 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