Senior Backend Engineer - Java/Kotlin (x/f/m)

Set a new pulse for healthcare!

We are looking for a Senior Backend Engineer to join the IAM (Identity and Access Management) team in Platform Services Tech.

Your mission will be to secure and scale the authentication capabilities that millions of Doctolib users rely on every day. You will drive the most impactful phases of a critical, multi-year migration to a self-hosted, Keycloak-based identity provider — a project at the intersection of platform engineering, security, and cross-team impact. Working in the tech team at Doctolib means building innovative products and features to improve the daily lives of care teams and patients.

What you'll do

Your responsibilities include but are not limited to:

Lead the next phases of the multi-year authentication migration to a self-hosted, Keycloak-based identity provider — completing token-based sign-in for Doctolib Pro apps and making the identity provider the single source of truth for user data

Own the reliability of high-traffic authentication systems end-to-end: monitoring, alerting, SLOs, incident resolution, post-mortems, and safe rollout practices (feature flags, canary releases, zero-downtime migrations)

Drive cross-team delivery independently: produce design documents and decision memos, build alignment across dependent teams, and make trade-offs explicit

Collaborate closely with the Product Security team on security-sensitive architecture decisions and changes

Contribute to frontend development in React and TypeScript on the custom interfaces tied to the IAM platform

Use AI tools daily to accelerate your own work and help establish repeatable AI-augmented workflows across the team

Who you are

Before you read on: if you don't have the exact profile described below, but you feel this job description matches your skill set, we still encourage you to apply.

You'll be a great fit if you

Have 7–10+ years of backend engineering experience with hands-on, daily Java or Kotlin development and a solid understanding of JVM internals (garbage collection, memory management, multi-threading, and profiling)

Have proven experience building and operating high-traffic production systems at scale — load testing, capacity planning, horizontal scaling, caching, and performance bottleneck identification

Own reliability end-to-end: you define monitoring, alerting, and SLOs, lead incident resolution, write post-mortems, and have shipped changes safely via feature flags, canary releases, and zero-downtime migrations on live systems

Have led complex, multi-week cross-team delivery independently — producing design docs, driving alignment across dependent teams, and making trade-offs explicit without waiting for consensus

Use AI tools daily in your engineering workflow, critically validate their outputs, and are excited to help establish shared AI practices for your team

Are fluent in English (written and spoken)

It would be fantastic if you

Have prior experience with identity providers (e.g. Keycloak), OAuth2, and/or OIDC

Have hands-on experience with security practices for exposed, high-traffic endpoints

Have contributed to frontend codebases in React and TypeScript

Have exposure to Kafka/CDC

Have exposure to mobile authentication

Life at Doctolib Tech

Our solutions are built on a single fully cloud-native platform that supports web and mobile app interfaces, multiple languages, and is adapted to country and healthcare specialty requirements.

Our stack is composed of Rails, TypeScript, Java, Python, Kotlin, Swift, and React Native.

We leverage AI ethically across our products to empower patients and health professionals. Discover our AI vision here.

Want to learn more about our tech culture and environment? Visit the Doctolib Tech site.

What we offer

A Deutschlandticket (Germany-wide public transport pass) fully paid for by Doctolib

28 vacation days + 1 additional day for each full calendar year of employment (up to a maximum of 30 days)

Work from abroad for up to 10 days per year thanks to our flexibility days policy