Engineering Team Lead, Sandbox

Mistral; Warszawa; On-site; PLN 300,000 - 600,000; Full time

Job summary

Mistral is seeking a people-leading senior infra architect to design and ship secure, scalable AI compute layers. You will balance architecture work with hands-on leadership, guiding a growing team of engineers building frontier AI systems.

You will drive secure, isolated environments, contribute to performance tuning, and partner with product to deliver reliable primitives for agents across Europe and beyond.

Qualifications

• 2+ years of people leadership experience.
• Deep Linux internals: namespaces, cgroups, seccomp.
• Shipped production systems in Go.
• Experience with network isolation at the packet level.
• 8+ years building backend or infrastructure systems.

Responsibilities

• Build the isolation layer: microVMs or containers, namespaces, cgroups, seccomp.
• Own the security boundary to keep customer code safe.
• Scale fleets: creation latency, density, lifecycle management for thousands of environments.
• Write Go and own architecture decisions for the hardest implementations.
• Grow engineers and coach them to take ownership.
• Manage the team: hiring, performance, growth paths, feedback.
• Collaborate with Product Managers to turn frontier research into primitives.

Skills

People leadership

Go

Linux internals

MicroVMs

Network isolation

Backend infra

Tools

Go

Linux

Firecracker

Job description

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.

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 team

Mistral is building a sovereign AI cloud for Europe. Our customers in finance, healthcare, and the public sector run frontier models on European-jurisdiction infrastructure, and the Cloud Platform team builds the systems that make that possible - compute orchestration, Kubernetes, bare metal, storage, networking, and the datacenter fleet that runs it all.

We run it all on our own metal, our own network, our own datacenters - which means when something breaks, the fix is ours to write.

European Compute Units let enterprises commit to multi-year capacity on that infrastructure, and we are scaling toward a gigawatt of compute across Europe by 2030. You will design and ship the layer every sovereign AI deployment depends on and shape the team building it.

The Role

This is a people-leadership role from day one. You will manage the team - hiring, coaching, performance, growth paths, honest feedback - while staying close to the code: roughly half your time in architecture decisions and the hardest technical problems the team faces, the other half leading your squad. If you are looking for a senior IC role, this is not it.

AI agents don't run in browsers. They run in sandboxes - and you will lead the team building ours.

We build secure, isolated, network-controlled environments with snapshotting primitives, designed for AI agents and reinforcement-learning workloads. An RL training run doesn't need one environment; it needs thousands, created and destroyed every second. An agent needs to sandboxed from the world while still feeling fast enough to be useful. That tension - airtight isolation, at fleet scale, at low latency - is the product.

Your customers are the people building the next generation of AI software on our infrastructure; the primitives you ship become the runtime their agents live in.

What You Will Do

• Build the isolation layer: microVMs or containers, namespaces, cgroups, seccomp, snapshot and restore.
• Own the security boundary. Customers run code they didn't write and can't fully trust - your systems make that safe.
• Scale to fleets: creation latency, density, and lifecycle management for thousands of concurrent environments.
• Write Go alongside your team and own the architecture and the hardest implementation decisions.
• Grow the engineers, not just the software - set the standard for ownership and coach people past their comfort zone.
• Own people management for the team: hiring, performance, growth paths, and honest feedback.
• Partner with Product Managers to turn frontier research needs into shippable primitives.

What We're Looking For

• 2+ years of real people leadership. You have managed engineers - hired, coached, given honest feedback, and grown them. Hands-on contribution matters here, but this role is judged on the team you build and lead, not just the code you write.
• Deep Linux internals: namespaces, cgroups, seccomp, virtualization - ideally microVMs of the Firecracker class.
• You have shipped production systems in Go. Not dabbled. Shipped.
• You understand network isolation at the packet level - not just firewall rules.
• Performance instincts: you know what a syscall costs, and you have the profiles to prove you've cared.
• 8+ years building backend or infrastructure systems.
• You have partnered with product, design, and business teams to ship software that reached real users.
• A low-ego, team-first mindset. We care less about your exact domain and more about whether you are the kind of technical force other engineers want to work alongside.

What we offer

We offer a comprehensive benefits package designed to support your well-being, growth, and work-life balance. Benefits vary by country and may include healthcare coverage, parental leave, retirement plans, relocation support, wellness programs, meal and transportation allowances, and other location-specific perks. For the most up-to-date details on benefits available in your location, please refer to our Benefits page.

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