Senior Performance Engineer

Overview 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 email 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. Our work impacts hundreds of millions of lives, from activists on the front lines defending freedom to leaders in governments protecting sensitive data; 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. We value intelligence, learning, potential and ambition in our hiring process. Adaptability is key as we navigate uncharted territories and redefine how business is conducted online. Hiring at Proton is highly selective, with less than 1% of candidates hired. We believe smaller teams of exceptional talent will always prevail over larger teams with lower talent density. 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 global 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. Tired of blending into the crowd? Join us and do work you can truly be proud of. Check our open‑source projects here The team 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. Responsibilities 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. Job Requirements & Technical Skills 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) and performance profiling tools. Proven ability to analyze latency, throughput and stability metrics across multiple layers (client OS, transport, application). Proficiency in Python (or similar scripting language) for scripting and/or Rust/C/C++ for benchmarking or systems analysis. Familiarity with network emulation and simulation tools (e.g. tc/netem, iperf, IPTables/nfTables). Experience with monitoring and observability stacks (Grafana, Prometheus, Loki) and CI/CD pipelines. Cross‑platform experience with Linux, macOS, Windows, Android and iOS preferred. Soft Skills Analytical and methodical yet creative in solving complex performance problems. Comfortable working with uncertainty and non‑deterministic conditions. Collaborative mindset able to work across client infrastructure and data teams. Strong communication and documentation skills in English. What We Offer Office First: Collaboration is easier and more effective in person, which is why we have offices in Geneva, Zurich, Prague, Barcelona, Paris, London, Vilnius, Skopje and Taipei. You can also work 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. Food: Lunch and snacks are provided by Proton every day at our offices. Transport: We will always support our employees with transport costs by subsidizing public transport, bike allowances or parking spaces based on your office location. Stock Options: At Proton we are all owners of the company and you get stock options when you join us. Flexible Working: You can define your own working hours as long as it works with team meetings. Learning and Development: We are committed to your professional growth. Proton offers various learning opportunities including training programs, conferences and events and continual learning. Employee Benefits: Comprehensive health insurance plans, competitive retirement savings options, generous vacation and leave policies and wellness programs. Work that Matters: Proton is a community‑first organization started with the support of a crowdfunding campaign and built with community input. To this day, Proton’s only source of revenue is user subscriptions. Over 100 million people trust and support Proton and we put our users and community first in everything we do. Read more about our impact here. Our Commitment to Diversity and Inclusion At Proton we believe diversity drives innovation and strengthens our mission to provide privacy as a default for all. 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, your information is stored in Greenhouse in accordance with their Service Privacy policy. 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 [email protected] 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. #J-18808-Ljbffr