About Sonio

Each year, 140M children are born. Birth defects affect 1 in 33 births in developed countries, and in 50% of cases, they are not detected during prenatal examinations. Prenatal medicine is particularly complex, and the scans impose heavy responsibilities on healthcare professionals. They can also be a source of stress for future parents.

Resulting from 5 years of collaboration between world-renowned experts from Necker Hospital and Ecole Polytechnique, Sonio uses artificial intelligence to improve prenatal screening and diagnosis. Based on patented algorithms and a proprietary expert database, Sonio aims to become the reference tool to help practitioners improve screening, reduce diagnostic errors, and optimize pregnant women’s medical path.

Sonio's mission is to improve women's and children's health by promoting access and quality of care through technological innovation, medical expertise, and collective intelligence.

About the role

As a Staff Engineer at Sonio, you will be the ultimate technical authority for our Elixir/Phoenix ecosystem. You will join one of our squads led by Romain (Engineering Manager), which houses the core of our backend codebase.

In this role, you will architect high-scale, resilient systems and arbitrate complex technical decisions to ensure the platform remains performant as we grow. You act as a force multiplier, driving engineering velocity across your squad through strategic design, clear communication, and deep-tier problem-solving.

Your main missions:

• Be the in-house Elixir / Phoenix expert squads rely on for the deepest problems

• Drive architecture for scale: concurrency, fault tolerance, clustering, back-pressure, recovery patterns

• Own the hardest problems end-to-end—from scoping and design to implementation—while distributing knowledge across the team.

• Author RFCs / ADRs for cross-squad changes and review others' designs

• Drive the refactors and tech-debt reductions that unlock velocity

• Grow the team through pairing, code reviews, design reviews and internal talks

• Contribute to senior / staff hiring (case design, tech deep-dives)

You'll join a growing engineering team with real room to shape how we build.

About the profile

Sonio is a mission-driven company, so interest in our mission is critical. Other requirements are:

• 8+ years of software engineering, with 3+ years in Elixir in production at scale (real bottlenecks debugged)

• You have expertise in web & cloud native environment,

• Deep BEAM mastery: GenServers, Phoenix, Ecto / PostgreSQL performance

• Distributed systems in a cloud context: fault tolerance, clustering, consistency/availability trade-offs, back-pressure, and recovery

• Strong architecture and API design; comfortable with event-driven, data-intensive systems

• Written communication is strong enough to author RFCs / ADRs that others use as a reference

• Technical leadership without authority: drives consensus across squads, mentors peers

• Fluent English; French a plus

• Bonus: experience in a regulated environment (medical devices, fintech…), React / TypeScript familiarity

Location: with have offices in Paris but this position can work in remote (ability to come to Paris every 1–1.5 months)

Salary: €85k – €100k + 10% bonus

We move fast and aspire to be transparent over the process - our objective is that the process from the first chat to an offer is no longer than a month. We also aspire to give an answer to every application in a week - if you have not heard from us, please follow up at [email protected].