Fullstack Software Engineer

About Proton

Join Proton and build a better internet where privacy is the default

Proton was founded in 2014 by scientists from CERN on a simple truth: privacy is a fundamental human right. Since then, we’ve built the world’s largest encrypted email service (Proton Mail) and expanded into Proton VPN, Proton Drive, Proton Pass, and Proton Calendar—tools used by millions globally to protect their freedom, fight censorship, and keep their data safe. In some situations, Proton has literally helped save lives!

We are profitable, independent (no VC control), and selectively hire from the top ~1% of applicants. Our 500+ team members across 50+ countries come from leading organizations and elite academic backgrounds. We move fast, keep hierarchy light, and prioritize impact over optics. If you want to do meaningful work with exceptionally high-caliber people, this is it. Join us and do work you can truly be proud of. Check our open-source projects here!

The team

MSA is a highly multi-disciplinary group started in 2019 to tackle difficult mail delivery, spam, abuse, and account security problems that impact the Proton ecosystem. We built sophisticated systems from scratch that combine big data, human intelligence, machine learning, and AI agents to make tens of millions of realtime or asynchronous decisions each day. Our custom systems have reduced spam filter misclassifications by over 80% and protected millions of users from account compromise by attackers. In order to move fast with limited resources, we are organized into autonomous teams responsible for the whole system, with fullstack expertise across infrastructure, data storage, backend, frontend, machine learning, and AI agents. We are looking for humble, mission-driven, systems-thinking people who want to make a big impact in a startup environment.

What you will do

MSA builds and operates services responsible for different domains. You will:

• work with other engineers and analysts to design, build, and operate these systems

• work on user-facing features involving frontend and backend software development

• You will have the opportunity to play Product or Project Managers roles and lead the whole planning and development process

• be responsible for the operational excellence of the systems/features and their interaction with other systems

• You may work on MSA's custom systems written in Python or on the Proton API written in PHP or on Web apps written in React