About the role

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

Company health insurance with great supplementary benefits through our partner Allianz

Company pension scheme (bAV) through Allianz with an employer subsidy of 40% (15% within the probationary period)

The Doctolib Parent Care program, which includes one month additional parental leave and much more

Enrollment in Doctolib's long-term employee value sharing plan called DoctoGrowth

Free mental health and coaching services through our partner Moka.care

Subsidized sports membership through our partner Urban Sports Club

A flexible workplace policy offering both hybrid and office-based mode

Alongside healthy snacks and our regular breakfast buffet, we provide a subsidized meal benefit

For caregivers and workers with disabilities, a package including an adaptation of the remote policy, extra days off for medical reasons, and psychological support

Access to the best AI tools for coding, development and dedicated training

Our interview process
TA Screen

Coding interview

System Design Interview

Behavioural Peer Interview

We want your experience to be clear, respectful, and transparent. Learn more about our hiring process on our candidate experience page.

Job details
Permanent position

Full-time

Berlin, Germany

Hybrid work setup (up to 2 remote days per week)

Start date: as soon as possible

We welcome everyone
At Doctolib, we are committed to improving access to healthcare for everyone. This translates into our recruitment process. We evaluate candidates based solely on qualifications and motivation, without any form of discrimination.
The more diverse ideas are heard, the more our product will truly improve healthcare for all. You are welcome to apply to Doctolib, regardless of your gender, religion, age, sexual orientation, ethnicity, or disability.
To ensure equal opportunities, we invite you to exclude personal information (e.g., pictures, age) from your applications. If you require any accommodation, please let us know for support during the hiring process.
Join us in building the healthcare we all dream of!

Your data privacy
All information provided is processed by Doctolib for application management. For data processing details, click here: France. Please contact hr.dataprivacy(at)doctolib.com for inquiries or to exercise your rights.

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Interview prep

Walk in with sharper answers.

Use these suggested prompts to prepare. They are not questions supplied by the employer.

Mid

Technology & IT Human Resources Javascript Python Remote Collaboration Mid level full-time

Practice questions

Tell us about work you have done that is close to the Senior Backend Engineer - Java/Kotlin (x/f/m) role.
How would you approach your first 30 days at Doctolib?
Which of Human Resources, Javascript and Python have you used recently, and what did it help you achieve?
Describe a time you solved a problem without waiting to be told exactly what to do.
How do you handle busy days, changing priorities, or pressure at work?

Prepare before the call

A recent example that proves your experience with Human Resources, Javascript and Python.
One short story with a problem, your action, and the result.
Two examples that show the strengths listed on your CV.
A clear reason why this role and company interest you.
Your availability, preferred work style, and salary expectations.

Ask them

What would success look like in the first 90 days?
What are the main problems this hire should help solve?
How does the team give feedback and measure good work?
What does a normal working week look like for this role?

Practice line

I am interested in the Senior Backend Engineer - Java/Kotlin (x/f/m) role at Doctolib. My relevant experience is [your example], where I [your action] and achieved [your result].