Senior Backend Engineer (Foundation)

Proton; Greater London; On-site; GBP 90,000 - 130,000; Full time

Benefits offered by this job

Stock options

Flexible working

Health coverage

Lunch and snacks

Transport support

Learning & development

Job summary

Proton is seeking a backend engineer to design and build shared libraries and internal services used across Proton products. You will shape architecture, write clear documentation, and collaborate with product teams to drive adoption in a fast-moving, privacy-focused environment.

You will work on a large-scale PHP backend with Rust components where performance and memory safety are critical, participating in RFCs and cross-team reviews while improving build times and developer experience.

Qualifications

• 5+ years building and operating backend systems in production.
• Working knowledge of Rust, or ability to learn quickly.
• Genuine taste in API design and ownership decisions of libraries vs services.
• Experience with codebases that are large enough for module boundaries to matter.
• Security-minded approach to abstractions and misuse.
• Ability to evolve shared code without breaking dependents.

Responsibilities

• Design and build shared libraries, framework layers, and internal services used across Proton products.
• 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 and design reviews, occasional PRs between repos.
• Work closely with other developers to help integrate libraries seamlessly into applications.

Skills

Backend development

PHP

Rust

API design

Monorepo

Security mindset

Architecture

Job description

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 Foundation Team

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. If several teams need it, it should exist once, and be good. 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 — we care that you understand ownership and lifetimes
• Genuine taste in API design. You have opinions about naming, defaults, error handling, and what belongs in a library versus a service
• A feel for architecture at codebase scale — you have worked somewhere large enough that module boundaries and dependency direction mattered, and you have views on what keeps a monorepo healthy
• Experience evolving shared code that other teams depend on, and doing it without breaking them
• A security mindset. You think about how the abstraction you just wrote will be misused
• The influence to get an internal library adopted rather than worked around, and the patience to carry a design through disagreement between two teams who both think they're right

Bonus points for

• Domain-Driven Design, or similar experience modelling complex domains where the boundaries matter
• 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. We answer only to our users — not advertisers, not investors with conflicting agendas, not governments. The work you do here is real, and the impact is measurable. (read more about our impact here)
• Work with smart and dedicated people - Our team is diverse, collaborative, and tight-knit with people coming from all walks of life, including many of the world’s top academic institutions and organizations, such as MIT, Harvard, Stanford, Caltech, Cambridge, and ETH.
• Technology: you'll get the right hardware and the right software you need to do your best work.
• Learning & Development: we invest in your growth because sharp people make us better. Proton is one of the fastest ways to accelerate your career because you'll be thrown into real challenges, with real ownership, from day one.
• Employee Benefits: your wellbeing isn't an afterthought. We offer strong health coverage, solid retirement options, generous leave, and wellness support so you can bring your best self to work every day
• Stock Options: at Proton, we all have the opportunity to be owners of the company. From day one, you have a real stake in what we're building. When Proton wins, you win.
• In-Person Collaboration: Amazing things happen when passionate, smart, and purposeful people get together in the same room. With offices across Geneva, Zürich, Barcelona, London and more, you'll spend most of your time collaborating face-to-face with people who genuinely care about what they're building
• Food: Lunch and snacks are on us every day in our offices so you can focus on the work and not on what's for lunch.
• Transport: getting to the office shouldn't cost you. We cover public transport, bike allowances, or parking, whichever works for you.
• Flexible Working: you own your schedule. Set hours that work for you and your team — because outcomes matter more than when the clock says you started.

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 (Proton, we, us, or our), your information is stored in Greenhouse, in accordance with their Service Privacy Policy. This 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 [e-mail].

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.