Research Engineer, Sandboxes

About this role

About Mistral Mistral provides full-stack AI solutions: from frontier models to developer tools, applications, and compute. We partner with enterprises tackling the hardest problems across high-stakes industries like finance, manufacturing, defense, healthcare, and the public sector, co-creating customized AI systems that they can run on their terms. We are a dynamic, collaborative team passionate about AI and its potential to transform society.

Our diverse workforce thrives in competitive environments and is committed to driving innovation. Our teams are distributed between Europe, North America, Asia and the Middle East. We are creative, low-ego and team-spirited. The Role As a Research Software Engineer on the Sandboxes team, you will design, build, and operate the platform that runs isolated environments for untrusted code at massive scale. Our work spans distributed systems, low-level virtualization, and product-minded platform design.

Engineers on this team move between deep infrastructure work and understanding how researchers actually use the platform. This is a software engineering role, not an ML research role. You do not need prior ML experience; what matters is writing clean, reliable systems code that scales. You will join a small, senior team where the wrong hire is worse than no hire. What You Will Do Design, build, and operate the sandboxing platform that runs untrusted code at scale across multiple Kubernetes clusters, from our own bare metal data centers to hyperscalers.

Develop the sandbox runtime leveraging Firecracker, enabling fast startup, snapshotting, and efficient scheduling without blocking expensive hardware. Obsess over performance and latency optimisation allowing us to reach millions of concurrent sandboxes. Write robust, well-tested systems code in Rust and Python; review code, CI/CD, and observability across the platform. Own cross-cluster networking, security boundaries, isolation guarantees and monitoring for suspicious activity.

Collaborate with researchers and ML engineers who use sandboxes for synthetic data generation and RL training, turning their needs into platform features. What We're Looking For A strong background in software engineering and distributed systems, with experience building and operating large-scale infrastructure. Deep expertise in at least one of: Kubernetes and cluster operations, cross-cluster networking, observability, or low-level virtualization.