Senior Backend Engineer - Platform (Inbox)

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 700+ 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!

Our business unit, Inbox, is a cross-functional team of about 60 engineers, product managers, designers, and data analysts driving the development of Proton Mail, the company's flagship product, and Proton Calendar. Our mission is to create an end-to-end encrypted solution with a better user experience than any other productivity product on the market. It is not always an easy journey, but it is one that offers the chance to create meaningful impact and drive lasting change.

The Platform team is a subteam of Inbox, responsible for the core components reused across Mail and Calendar. Rather than owning a single feature, the team builds the shared foundations, the tooling and systems other Inbox teams build on top of, so that Mail and Calendar can scale reliably. Over the next year, the team's priority is efficiency and cost reduction.

The Platform team is partnering with the product team on new systems, such as how client apps receive updates from the server (e.g. new email and calendar event delivery), while also improving the performance of systems already in production. Quality and performance are treated as first-class concerns in everything the team ships, not an afterthought.

As a Senior Backend Engineer on the Platform team, you'll bring hands-on experience with data-driven delivery, monitoring, and how the team plans and prioritizes its work. You'll work closely with the product team to design new systems, and with the rest of the team to improve the performance of what's already running.

• →Architect and develop core systems: Design and build core, cross-product systems shared by Proton Mail and Calendar, with scale and cost-efficiency as first-class constraints.
• →Performance: Improve the performance of existing systems, using monitoring and metrics to identify where time and infrastructure spend are going and where to cut. Drive cost-reduction and efficiency initiatives across shared platform components, from proposal to production
• →Data-driven delivery: Bring a data-driven approach to technical decisions and delivery planning, shaping how the team measures and prioritizes its work
• →Collaboration: Work closely with a team of backend and clients engineers, with a strong emphasis on quality and performance in everything shipped
• →Testing: Develop and implement comprehensive testing strategies, including unit tests and integration tests, to ensure the reliability of core systems.

• Strong experience in backend development, with a track record of designing, building and scaling systems that serve a large user base (100M+)
• Demonstrated ability to improve the performance and cost-efficiency of systems already in production
• Hands-on experience with monitoring and observability tooling (e.g. Grafana, OpenTelemetry, or equivalent), and a data-driven approach
• Solid understanding of SQL (MySQL preferred) and data modeling
• Experience leading a technical initiative end-to-end, from design through production

• Experience with client-server sync or push-notification systems
• Experience with Kubernetes or other containerization technologies
• Experience with PHP/Symfony, Rust, or Python
• Full-stack experience, comfortable working across the frontend as well as the backend

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Compensation range
 Paris : 54,000€ - 83,000€ gross annually*

Other locations: Compensation will be discussed during the interview process
*Final compensation will be determined based on the candidate's qualifications, skills, and previous experience