Senior Backend Engineer (Foundation)

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. 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 prioritise impact over optics. If you want to do meaningful work with exceptionally high-calibre people, this is it.

The Foundation team builds what the product teams build on: the shared backend framework, the internal libraries, the common services and abstractions that every Proton application reaches for. You will work in PHP for API related work, and in Rust for components where performance and memory safety justify it or for microservices. You will own libraries or initiatives end to end: design, implementation, documentation, versioning, and the migration path for everyone already depending on the old version. Architecture is a large part of this role. Many engineers work in the same monorepo, which means module boundaries, dependency direction, and ownership are not academic concerns — they decide whether the codebase stays navigable or slowly turns into something nobody can change safely. You will help define those boundaries, make the structural calls that keep teams from stepping on each other, and do some work to enforce them: writing the RFC, adding rules, untangling the cycle that shouldn't have been there. None of this happens in isolation. You will work closely with other teams who consume and use what you build.

What you will do:

• Design and build shared libraries, framework layers, and internal services used across every Proton product.
• Turn recurring patterns into good abstractions.
• Write documentation and examples people actually use, and treat adoption as part of shipping.
• Improve the day-to-day: build times, local dev setup, test ergonomics, debuggability, developer experience.
• Work in the open with product teams — RFCs, design reviews, and the occasional pull request into someone else's repo to show what you mean.
• Work closely with other developers to help integrate libraries seamlessly into applications.

Job requirements:

• 5+ years building and operating backend systems in production, including code you stayed responsible for long after launch, with a focus on modern PHP.
• Working knowledge of Rust, or clear evidence you can get there quickly.
• Genuine taste in API design.
• A feel for architecture at codebase scale.
• Experience evolving shared code that other teams depend on, and doing it without breaking them.
• A security mindset.
• The influence to get an internal library adopted rather than worked around.

Bonus points for:

• Domain-Driven Design, or similar experience modelling complex domains.
• Background in developer tooling, platform, or DX teams.
• Contributions to open source, especially libraries with real users.
• Experience migrating a codebase incrementally between architectures or languages.
• Experience with applied cryptography, key management, or end-to-end encrypted systems.
• Experience with building CI/CD.

What We Offer:

• Work that Matters: millions of people trust Proton with their privacy.
• Work with smart and dedicated people - Our team is diverse, collaborative, and tight-knit.
• Technology: you'll get the right hardware and software you need to do your best work.
• Learning & Development: we invest in your growth.
• Employee Benefits: strong health coverage, solid retirement options, generous leave, and wellness support.
• Stock Options: at Proton, we all have the opportunity to be owners of the company.
• In-Person Collaboration: amazing things happen when passionate, smart, and purposeful people get together.
• Food: lunch and snacks are on us every day in our offices.
• Transport: we cover public transport, bike allowances, or parking.
• Flexible Working: you own your schedule.

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 feel valued and empowered.