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Research Engineer, Sandboxes

Mistral - London, United Kingdom - In-office

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Mistral is building full-stack AI solutions spanning frontier models, developer tools, applications, and compute infrastructure. The company partners with enterprises across finance, manufacturing, defense, healthcare, and the public sector to co-create customized AI systems. 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. This is a software engineering role focused on distributed systems, low-level virtualization, and product-minded platform design—not ML research. You do not need prior ML experience; what matters is writing clean, reliable systems code that scales. You will join a small, senior team. Key responsibilities: - Design, build, and operate the sandboxing platform running untrusted code at scale across multiple Kubernetes clusters, from bare metal data centers to hyperscalers - Develop the sandbox runtime leveraging Firecracker, enabling fast startup, snapshotting, and efficient scheduling - Obsess over performance and latency optimization 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, translating their needs into platform features Requirements: - 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 - Fluency in Python or Rust; comfortable writing systems code where performance and security matter - Strong software-design instincts: modular code, testing, CI/CD, observability, and a bias for reliability - Self-starter who learns fast; core skills matter more than specific tools - Low-ego, collaborative, and comfortable with ambiguity in a small, high-ownership team Nice-to-haves: - Experience with Firecracker, microVMs, or similar virtualization technologies - Product-mindedness: understanding of how sandboxes are used for synthetic data generation or RL training - Experience with GPU clusters, CUDA, or ML workloads - Prior SRE or platform engineering experience at scale - Open-source contributions or widely used internal tools

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