Software Engineer, Windows (VPN)

Location: Barcelona, Spain or Vilnius, Lithuania; onsite collaboration required

Salary: €37,100–€68,000 gross annually in Barcelona; €33,800–€64,000 gross annually in Vilnius

Company

Proton develops privacy-focused products including Proton Mail, Proton VPN, Proton Drive, Proton Pass, and Proton Calendar.

What you will do

• Design, build, maintain, and evolve Proton’s Windows VPN applications.
• Contribute across the application lifecycle, including feature design, implementation, deployment, monitoring, and incident response.
• Integrate cross-platform logical core libraries written in Rust.
• Define, maintain, and improve unit, integration, and automated GUI testing with FlaUI.
• Collaborate with product managers and engineers to deliver privacy-preserving products used by millions of people.
• Configure CI/CD pipelines and support gradual rollouts and operational observability.

Requirements

• Strong experience with C# and .NET development.
• Experience building and maintaining Windows desktop applications with WinUI, WPF, or similar frameworks.
• Understanding of MVVM, dependency injection, asynchronous programming, and event-based messaging.
• Experience writing maintainable, well-tested, scalable code and driving complex technical projects.
• Knowledge of networking fundamentals, including TCP/IP, DNS, and routing concepts, with an interest in VPN technologies.
• Experience with Windows debugging, profiling, performance optimization, Git workflows, GitLab CI/CD, telemetry, metrics, monitoring, and alerting.

Nice to have

• Rust development experience.
• Appreciation for user experience and design quality.

Culture & Benefits

• Mission-driven work focused on privacy and open-source technology.
• Collaborative, diverse teams with lightweight hierarchy and substantial ownership.
• Health coverage, retirement options, generous leave, and wellness support.
• Learning and development investment, suitable hardware, and stock options.
• Flexible working hours with in-person collaboration at company offices.
• Office meals and support for public transport, cycling, or parking.