Software Engineer, Windows (VPN)

Proton, a privacy‑focused technology company founded by CERN scientists, builds encrypted services such as Proton Mail, Proton VPN, Proton Drive, Proton Pass and Proton Calendar. The team is independent, profitable and operates globally with more than 500 employees. The opening is for a Software Engineer on the Windows VPN squad, tasked with creating and evolving Proton's Windows applications that protect millions of users worldwide. In this role you will design, implement and maintain the full lifecycle of Windows‑based VPN software. Daily work includes writing new features, configuring CI/CD pipelines, deploying releases, monitoring performance and responding to operational incidents. You will also shape the testing framework, unit, integration and automated GUI tests using tools like FlaUI, while collaborating closely with product managers and engineers across the organization to ensure privacy‑preserving outcomes. The position requires deep expertise in C# and the .NET ecosystem, as well as proven experience building Windows desktop applications with frameworks such as WinUI or WPF. Candidates must understand MVVM architecture, dependency injection, asynchronous programming (async/await) and event‑based messaging, and be capable of delivering maintainable, well‑tested, scalable code. A track record of driving organisational change and leading complex technical projects is essential, alongside a solid grasp of software architecture, engineering best practices and a keen eye for user‑experience and design quality. Applicants should also possess working knowledge of networking fundamentals (TCP/IP, DNS, routing) and an interest in VPN technologies, plus experience in debugging, profiling and performance optimisation on Windows. Familiarity with Git‑based workflows, GitLab CI/CD pipelines, gradual rollout strategies and observability tooling (telemetry, metrics, monitoring, alerting) is also required. While not mandatory, experience with Rust is considered a strong plus. The role is fully remote‑friendly, allowing you to join a high‑calibre, fast‑moving team that values impact over hierarchy. Proton offers the chance to work on products that matter to millions, with a culture that prizes privacy, open‑source contributions and meaningful, measurable outcomes. What the role asks for: - Strong C# and .NET development experience - Strong Windows desktop app experience (WinUI/WPF) - Solid MVVM, DI, async/await, event‑messaging knowledge - Ability to write maintainable, well‑tested, scalable code - Experience driving change and leading complex projects - Strong software architecture and engineering best‑practice understanding - Appreciation for user experience and design quality - Working knowledge of TCP/IP, DNS, routing, VPN concepts - Experience debugging, profiling, performance tuning on Windows - Familiarity with Git workflows and GitLab CI/CD pipelines - Experience with gradual rollout and observability tooling - Rust programming experience (nice‑to‑have)