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Agent guide: [/agents.md](https://www.wearedevelopers.com/agents.md). --- # Software Engineer - **Company:** Proton - **Location:** Madrid, Spain - **Contract:** Permanent contract - **Skills:** .NET Framework, Microsoft Windows, Application Lifecycle Management, Unit Testing, C Sharp (Programming Language), Profiling, Software Quality, Continuous Integration, Software Debugging, Dependency Injection, Domain Name System (DNS), Extensible Application Markup Language, Virtual Private Networks (VPN), Windows Presentation Foundation, Model View ViewModel, Networking Basics, Routing, Performance Tuning, Software Architecture, Remote Access Technology, Systems Integration, TCP/IP, Windows Desktop, Datadog, Gitlab, Git Flow, Integration Tests, Asynchronous Programming - **Published:** September 8, 2026 - **Apply:** https://www.adzuna.es/contact-us.html ## About the Role Strong experience building and maintaining Windows desktop applications using frameworks such as WinUI, WPF, or similar. Solid understanding of MVVM architecture, dependency injection, asynchronous programming (async/await), and event?based messaging patterns. Proven ability to write maintainable, well?tested, and scalable codebases. Demonstrated experience driving change within an organization and leading complex technical projects A strong understanding of software architecture and engineering best practices. An appreciation for user experience and design quality. Rust experience is not required but is a significant plus. Working knowledge of networking fundamentals (TCP/IP, DNS, routing concepts) and an interest in VPN technologies and protocols. Experience with code debugging, profiling, and performance optimization on Windows. Familiarity with Git-based workflows, CI/CD pipelines (GitLab) and modern collaborative development practices. Experience with gradual rollout, and observability tooling (telemetry, metrics, monitoring and alerting). Even if you don't meet every requirement listed above, if you're passionate about privacy and believe you could be a great fit, we encourage you to apply. ## Description The role: As an engineer on our small Windows VPN team, you will be responsible for designing, building, maintaining, and evolving Proton's applications on Windows. You will be involved in the entire application lifecycle, from feature design and implementation to CI/CD configuration, deployment, monitoring, and operational incident response. You will collaborate closely with product managers and engineers across the company to deliver privacy?preserving products used by millions of people worldwide. Our codebase is primarily written in . NET and WinUI (C#/XAML), and we are building and integrating cross?platform logical core libraries written in Rust. Software quality is central to this role. You will help define, maintain, and improve our testing stack, which includes unit tests, integration tests, and automated GUI tests (using FlaUI). What we are looking for: Strong experience in C# and ., We are committed to fostering an inclusive environment where all individuals, regardless of race, ethnicity, gender, age, sexual orientation, physical ability, or socio-economic background, feel valued and empowered. We strive to create equal opportunities, promote open dialogue, and support continuous learning to ensure every voice is heard and respected. If you need any extra support or reasonable adjustments during the hiring process, please let your talent partner know. Candidate Privacy Notice When you apply for a position, refer a candidate, or are considered for a role at Proton Technologies AG (Proton, we, us, or our), your information is stored in Greenhouse, in accordance with their Service Privacy Policy. This information is used to evaluate your suitability for the posted position. We also retain this information for consideration for future roles that you may apply for or that we believe may align with your background and skills. If we no longer have a legitimate business need to process your information, we will either delete or anonymize it. Should you have any inquiries about how we use or manage your information, or if you wish to access, correct, or delete your data, please contact our privacy team at ******. Proton does not accept unsolicited resumes from any sources other than directly from candidates. We will not pay a fee for any placement resulting from an unsolicited offer, even if the candidate is subsequently hired by Proton. To learn more about our privacy policy, please visit our privacy policy page. Compensation Range Barcelona: 37,********,000 EUR gross annually* Vilnius: 33,********,000 EUR gross annually* Final compensation will be determined based on the candidate's qualifications, skills, and previous experience. #J-*****-Ljbffr Inscribirse en esta oferta Recibir ofertas similares por correo electrónico Al crear una alerta, aceptas nuestros Términos y condiciones y Política de privacidad, y el uso de cookies.