Senior Backend Engineer (Foundation)

Proton, a privacy‑focused technology firm founded by CERN researchers, delivers encrypted services such as email, VPN, cloud storage, password management and calendar tools used by millions worldwide. The Senior Backend Engineer (Foundation) will join the team that creates the core backend platform and reusable components that power every Proton product. In this position you will craft shared libraries, framework layers and internal services, turning repeated patterns into clean abstractions. Your work will include writing clear documentation and examples, improving developer ergonomics like build times and local environments, and collaborating openly through design proposals, reviews and occasional cross‑repo pull requests. You will also define module boundaries within the monorepo, set ownership rules, and help other squads integrate the new code safely. The role requires at least five years of experience building and maintaining production‑grade backend systems, primarily with modern PHP, and a solid grasp of Rust concepts such as ownership and lifetimes. You must possess a strong sense of API design, including naming, defaults and error handling, and have dealt with large‑scale codebases where module boundaries and dependency direction are critical. Experience evolving shared code without breaking downstream users and a security‑first attitude are essential, as is the ability to persuade teams to adopt internal libraries despite differing opinions. Additional advantages include familiarity with domain‑driven design, developer tooling or DX work, contributions to open‑source libraries, and exposure to cryptography or CI/CD pipelines. Proton offers a globally distributed, highly skilled team, generous health and retirement benefits, stock options, and office spaces in cities such as Geneva, Zürich, Barcelona and London where in‑person collaboration, meals and transport support are provided.