Backend Engineer

What You'll Actually Do

• Own integration quality end to end: catch issues before customers do, fix them, and make sure they can't recur.

• Build the tool gateway: turn every connected API and MCP into a clean Python SDK the agent composes, with routing, auth, rate limits, and reliability.

• Run the sandboxes: a persistent Linux environment per workspace, isolated, secured, autoscaled, and cheap per task.

• Own the data layer: state and persistence across tens of thousands of multi-tenant workspaces, durable and fast.

• Whatever needs building. Small team, large surface.

Why This Role Is Different

• No layers. You work directly with both founders, and decisions get made in the room, not in a Linear ticket.

• The backend is the ceiling. Every integration you make reliable and every sandbox you make cheaper raises what the whole agent can do.

• You're building the backend of a frontier harness: the layer that decides how much of the model's intelligence turns into real work.

Who You Are

• You design distributed systems for scale and reliability, and have operated them in production through the breakage.

• You know sandboxing and OS-level isolation cold: containers, Linux internals, running untrusted code safely.

• You've wrangled real integration plumbing: OAuth, webhooks, rate limits, and third-party APIs that lie.

• You think in multi-tenancy, durability, and cost per request, and design for failure by default.

• Security and blast radius are instincts you bring to every design, especially when the thing executes model-written code.

• You build with AI by default, because that's how the team moves.

• You may never have shipped an LLM feature, and that's fine. This is a systems role.

Even Better If

• You've worked on infrastructure, platform, or developer-tools teams where reliability was the product.

• You've built sandboxing, code-execution, or multi-tenant systems before.

• You're at home in agentic engineering workflows, spec to production.

• You've contributed to the open-source infrastructure the world runs on.

• You've founded something or been an early-stage builder.

Compensation

Top-of-the-market salary and the kind of ownership that only exists at this stage.

The best work happens when you're in the room. This role is Munich or Warsaw.