Principal Data Scientist

Sthenos AI
is the AI developer of EFA Group, building intelligent, mission-ready solutions for defense and aerospace. With deep expertise in Command-and-Control (C2), cyber defense, computer vision, and autonomous systems, we design and deploy secure, field-proven AI that enhances operational efficiency and situational awareness. As part of a leading European defense ecosystem, we bring scalable innovation where it matters most — in the theater of operations.

As a
Principal Data Scientist
(f/m/d) you shape and implement our data science strategy and innovation at Sthenos AI together with the CTO. You will assume technical leadership of several projects, ensuring our AI solutions are scientifically robust, operationally impactful and meet mission-critical needs in defence & security. You coach and mentor other data scientists, act as an architect for advanced modeling approaches, as well as serve the view of our data science to stakeholders from inside and outside the company.

• You are the architect of innovative data science solutions that assure model scalability, robustness, and reliability across domains.
• You own product-level modeling strategies end-to-end - research, prototyping, bringing models to production and operationalization / monitoring.
• You also define and advocate for best practices across the data science life cycle, aligned with Sthenos AI's MLOps operating model.
• You are a mentor and coach to both senior and seasoned data scientists, guiding the development of skills as well as quality and consistency across teams.
• You collaborate closely with ML engineers and Site Reliability engineers to define the company's analytical/AI infrastructure roadmap and technology portfolio, pushing readiness for next.
• You will help with Business development by advising on strategy and where there are market opportunities in which ΑΙ can give competitive edge.
• You work with public sector customers and partners to translate complex operational challenges into powerful, data-driven solutions.
• You'll lead exploration and adoption of new technologies (e.g., large-scale distributed LLM inference, fine-tuning of foundational models, simulation-based ML).
• You contribute to the definition of V&V (Verification & Validation) methods for AI models in safety- and mission-critical scenarios.
• You guarantee the secure and responsible use of AI for all projects.
• You are the ambassador for Sthenos AI in external conferences, expert committees and consortias, leading the thought leadership in defense-focused AI.

Your Skills

• PhD or equivalent graduate degree in Data Science / Machine Learning, Computer Science, Statistics, Informatics, or another quantitative field.
• 8+ years of experience in advanced data science / machine learning, with strong delivery of production-level solutions.
• Deep proficiency in Python and its ML ecosystem (Pandas, NumPy, PyTorch, TensorFlow, Hugging Face, etc.).
• Strong expertise in end-to-end ML workflows, including data engineering, model design, training, deployment, and lifecycle management.
• Proven experience in large-scale or distributed ML systems (Ray is a big plus, PyTorch Lightning, Horovod, or equivalent).
• Demonstrated experience with modern AI approaches in at least two of the following areas: large language models, computer vision, multimodal learning, generative AI.
• Hands-on experience integrating ML models into operational systems with real-time performance monitoring.
• Familiarity with cloud-native and high-performance computing environments (AWS, Azure, GCP, or on-prem HPC).
• Strong publication or patent record, or equivalent evidence of contribution to the AI community.
• Familiarity with defense, aerospace, or other mission-critical environments is highly advantageous.

Your Competencies

• Visionary and strategic thinker, able to align cutting-edge research with real-world mission needs.
• Strong leadership and mentoring skills; you inspire and elevate the performance of your peers and team.
• A rapid prototype builder, not afraid of demonstrating the possibilities of modern technology and newest frameworks.
• Ability to make sense out of ambiguity and clarity about the next steps in situations with many options.
• Excellent communicator, able to adapt complex scientific results for technical and non-technical audiences, including executives and government stakeholders.
• High resilience and adaptability, thriving in fast-paced and high-stakes environments.
• Deeply collaborative, with the ability to create alignment across cross-functional teams and partner organizations.

We Offer

• Competitive remuneration package
• Ticket vouchers and/or gas expense
• Private medical insurance package
• Continuous learning & development opportunities
• Participation in cultural and team-building activities
• Exposure to a growing environment with cutting-edge technologies
• Corporate wellness initiatives