Senior Software Engineer (AI/Python)

At Castor, we’re modernizing the backbone of clinical research

Clinical trials are the gatekeepers of human health, yet the industry is still bogged down by fragmented, manual processes that can waste time and exclude patient populations. At Castor, we are building the operating system for the next era of clinical research.

We provide a modular cloud platform designed to run trials end-to-end. Our foundation is a robust Electronic Data Capture (EDC) system, supported by eConsent for recruitment and screening and eCOA to accurately capture patient reported outcomes. We don’t just stop at data collection; we use Castor Catalyst (our high-precision AI automation) to strip away the manual effort that historically makes research slow and expensive.

How we work: Trust over tracking

We are a remote-first company built on the belief that talented people do their best work when they have the agency to manage their own lives. We believe that high performance requires a foundation of trust, health, and cutting-edge support.

• Work-life integration: We don't believe in performative presence. We trust you to own your schedule and show up for your team, while also making space for your life outside of work.
• Deep work & async: We protect your time. We prioritize thoughtful, asynchronous communication so you can focus on solving hard problems without a calendar full of status update meetings.
• Radical candor: We value the truth over hierarchy. We give and receive direct feedback because that’s how we grow—as individuals and as a company.

Your mission and impact

As a Senior Software Engineer (AI) in our Catalyst team you will be a key driver in building and scaling our AI-powered applications. You will work closely with other engineers to develop and implement innovative solutions.

Our stack includes Python 3.13 with FastAPI and the Haystack AI framework, using LLMs to extract clinical data from medical documents and FHIR resources. We host on Azure with Kubernetes and Argo CD, and are building a data pipeline on GCP.

As part of your role you will also take part in our on-call rotation.

Who are you

• You have 5+ years of software development experience.
• You enjoy being hands on, bringing new ideas and excitement to tackling challenging software problems.
• You deliver software efficiently while maintaining high engineering standards.
• You actively share expertise through design discussions, documentation, examples, and mentoring other engineers.
• You are a self-starter who masters the art of remote collaboration. You value deep work and asynchronous communication to drive results
• Giving and receiving feedback are necessary to win as a team. You give and receive direct, data-driven feedback, even when it’s uncomfortable.
  

What you’ll bring

• Extensive experience with modern-day Python and its ecosystem.
• Experience with messaging patterns, event-driven architectures, and integrating with external systems.
• Understanding and experience with asynchronous programming patterns.
• Proven experience with cloud applications (GCP) and a working knowledge of Kubernetes.
• Proven experience with using AI tooling and workflows to deliver high quality production grade code suitable for regulated environments.
• A passion for building AI applications and using AI assistants.
• A commitment to high code quality, comprehensive testing, operational robustness, and thorough code reviews.
• Familiarity with data pipelines or ETL processes (though you are not a dedicated Data Engineer).
• While not required, experience within life sciences, healthtech, or e-clinical products is a significant plus.
  

Accepting candidates +2/-2 CET. At this time, we cannot accept applications from France, Germany, Spain, Bulgaria, or Switzerland.

How we invest in you

High performance isn't sustainable without real support. We provide the infrastructure you need to stay healthy, focused, and rewarded.

• Rest is non-negotiable: Unlimited annual leave with 25-day minimum. We don’t just allow time off; we expect you to take it.
• Downtime weeks: Once a quarter, the whole company shifts gears. No new shipping—just a week for deep focus, learning, or catching up so we can start the next quarter fresh.
• AI-first culture: We provide the tools and training to ensure you’re spending your energy on high-value work, not manual repetition.
• Real ownership: All Castor team members are offered options through our Employee Stock Option Plan (ESOP).
• Comprehensive wellbeing: Free access to Open Up for mental health, specialized sleep courses (for you and your family), and a budget to make your home office a place you actually want to be.
• Annual bonus: A guaranteed "Happy Holidays" bonus every December.

Belonging at Castor

We build products to make research accessible to everyone, and we believe our team should reflect that same diversity.

Our remote setup is designed to support you as a whole person—your family, your mental health, and your authentic self.

We don't care about your background as much as we care about your perspective and your expertise. We strongly encourage applications from women, people of color, and the LGBTQ+ community. Please feel free to share the pronouns you use (for example she/her/hers, he/her/his, they/them/theirs, etc.).