Senior Site Reliability Engineer

**Why Thunderbird?** Thunderbird is one of the world’s most trusted open\-source email applications, empowering more than 20 million people globally. At MZLA, the team behind Thunderbird, we build privacy\-respecting communication tools that help people manage their digital lives while staying in control of their data. We are open source by design. Our products are developed transparently and in collaboration with a global community of contributors, and that same spirit shapes how we work: collaboratively, inclusively, and with a shared commitment to putting users first. Our small but growing distributed team includes 65\+ people across seven countries. As Thunderbird evolves beyond a single desktop application, we are expanding across desktop, mobile, and paid services to build independent, privacy\-respecting alternatives to big tech ecosystems. Our revenue model combines user donations, which help keep Thunderbird’s apps freely available, with paid services that cover the costs of hosted offerings while supporting long\-term sustainability and continued innovation. **A note about MZLA and Mozilla:** MZLA Technologies Corporation is the nonprofit\-owned company behind Thunderbird and part of the Mozilla family. MZLA is separate from Mozilla Corporation and has its own compensation programs, benefits, and employment policies. **The opportunity** The Senior Site Reliability Engineer establishes and maintains the infrastructure and operational systems that Thunderbird users and teams depend on every day. You'll design and develop CI/CD systems for MZLA websites, services, and release workflows, diagnose and debug production incidents, and implement improvements to enhance system reliability. We believe that good infrastructure work is invisible when it's going well and invaluable when it isn't. This role is for someone who treats production as something to be understood, not just kept running. You write things down, flag problems before they become fires, and leave documentation better than you found it. You bring production instincts, infrastructure\-as\-code fluency, and security awareness that's baked in, not bolted on. You'll work closely with Software Development Engineers, team members, and community contributors, reporting to the Sr Manager, Platform Infrastructure. This is a great opportunity for someone who thrives with ambiguity, makes good decisions without a complete picture, and cares about Thunderbird's mission: open\-source software used by millions who choose privacy and ownership over convenience. This role requires consistent overlap with Pacific Time zone working hours to enable effective collaboration. You should have availability for regular overlap hours for context sharing with Pacific Time colleagues. **What you’ll do** * Operate and evolve our EKS\-based Kubernetes platform, supporting service migrations, platform improvements, and reliability initiatives. * Design and develop CI/CD syst