Fullstack Software Engineer; Email Security & Anti-Abuse

Purpose of the role

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 human intelligence and machine learning to make tens of millions of realtime or asynchronous decisions each day. Our custom systems have reduced spam filter misclassifications by over 60%, blocked millions of abusive bulk signups, protected hundreds of thousands of users from account compromise by attackers, and mitigated hundreds of DDoS attacks.

In the last few years, we have also been building complicated new products, including launching Wallet, Lumo AI, and Meet. We are the main group at Proton working on AI. In order to move fast with limited resources, we are organized into autonomous teams responsible for the whole system, with expertise across infrastructure, data storage, backend, web and mobile apps, machine learning, security and operational excellence.

We are looking for humble, mission-driven, systems-thinking people who want to make a big impact in a startup environment.

• work with other engineers and analysts to design, build, and operate these systems
• work on special 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 main Proton API written in PHP or on Proton Web apps written in React or even on native iOS and Android mobile apps

• Deep experience with backend development (Python, PHP, or Go)
• Experience with frontend design and development (JavaScript, React, Typescript, or jQuery)
• Experience building complex production systems
• Experience with data processing and storage (MySQL, MongoDB, Redis, Kafka, Elastic, Ceph, Click House)
• Able to work autonomously and lead the whole development process, from design to QA
• Experience with AI tools and AI agents
• Excellent English communications, both written and spoken

• experience with machine learning and real-time prediction systems
• experience with iOS or Android app development
• experience with managing Linux servers, including infrastructure as code (Puppet, Ansible) and containerization

• 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 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.
• Food:Lunch and snacks are provided by Proton every day at our offices.
• Transport:We will always support our employees with transport costs through 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.

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.