Join Proton and build a better internet where privacy is the default
At Proton, we believe that privacy is a fundamental human right and the cornerstone of democracy. Since our inception in 2014, founded by a team of scientists from CERN, we have dedicated ourselves to providing free and open‑source technology to millions worldwide, ensuring access to privacy, security, and freedom online.
Our journey began with Proton Mail, the largest secure e‑mail service globally, and has since expanded to include Proton VPN, Proton Calendar, Proton Drive, and Proton Pass. These tools empower individuals and organizations to take control of their personal data, break away from Big Tech’s invasive practices, and defeat censorship. In some cases, Proton’s services have even been instrumental in saving lives by enabling secure and private communications in high‑risk situations.
Proton is a profitable company that does not rely upon VC funding, supporting over 100 million user accounts with a growing team of over 500 people from over 50 different countries, from the world's top companies and universities. Adaptability is key as we navigate uncharted territories and redefine how business is conducted online.
You will have the opportunity to work with many of the world's top minds in their fields, ranging from former international math and science olympiad winners to chess champions.
We have a integral mindset and big ambitions but remain a start‑up at heart. We value empowerment and flexibility and keep our structure flat to keep moving fast and avoid unnecessary politics. Proton VPN enables millions of people to connect securely and privately, even in places where the internet is restricted or unreliable. Delivering that experience means our service must perform flawlessly under highly variable, real‑world conditions.
We are looking for a Senior Performance Engineer to lead our efforts in making Proton VPN the fastest, most resilient, and most reliable VPN service in the world.
You will define and drive the measurement, analysis,



and optimization of Proton VPN’s end‑to‑end performance, across clients, platforms, and global infrastructure. You’ll help ensure that every connection is fast, stable, and private, regardless of where the user is or what network they’re on.
Design and own Proton VPN’s performance framework, defining metrics and KPIs that reflect the real‑world experience of users (time‑to‑connect, throughput, latency, stability, reconnection rates, etc.).
Develop distributed testing systems that simulate real network conditions, including low bandwidth, packet loss, and high‑latency scenarios.
Continuously measure and analyze performance across platforms (desktop, mobile, backend) and regions to identify bottlenecks and regressions.
Collaborate with backend, R&D;, and client teams to optimize protocol handling, connection setup, routing, and encryption performance.
Create dashboards, reports, and automated alerts to track global performance health.
Contribute to the design of resilient connectivity strategies that adapt dynamically to variable network conditions.
Serve as the performance champion within the engineering organization, mentoring others and driving a data‑driven performance culture.
5+ years of experience in performance engineering or systems QA, ideally in networking, VPNs, or distributed systems.
~ Knowledge of network protocols (TCP/IP, UDP, TLS, WireGuard, debugging, manipulating, and performance profiling tools.
~ Proficiency in Python (or similar scripting language).
~ Familiarity with network emulation and simulation tools (e.g.,



Experience with monitoring and observability stacks (Grafana, Prometheus, Loki) and CI/CD pipelines.
~ Cross‑platform experience with Linux, macOS, Windows, Android, and iOS preferred.

Experience with Rust/C/C++/System development

Analytical and methodical, yet creative in solving complex performance problems.
Collaborative mindset, able to work across client, infrastructure, and data teams.
Strong communication and documentation skills in English.
Office First: You can also enjoy working from home up to 30% of the time, while enjoying great company during our three core days in the office.
Technology: We provide all the devices and software you need to excel in your role, ensuring you have the best tools at your disposal to achieve your goals.
Transport: We will always support our employees with transport costs through subsidizing public transport, bike allowances, or parking spaces based on your office location.
Flexible Working: You can define your own working hours as long as it works with team meetings.
Learning and Development: Proton offers various learning opportunities, including training programs, conferences and events, and continual learning.
Comprehensive health insurance plans, competitive retirement savings options, generous vacation and leave policies, and wellness programs.
If you need any extra support or reasonable adjustments during the hiring process, please let your talent partner know.
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. 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.
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

📌 Senior Development Engineer (Barcelona)
🏢 Proton
📍 Barcelona