Backend Engineer

About the role

Work on Windmill's Rust backend - the execution engine, workers, language runtimes, API layer, and infrastructure that powers thousands of production deployments.

• Execution engine: scheduling, job queues, worker orchestration, flow execution with branching, parallelism, retries, and error handling.
• Language runtimes: maintain and extend sandboxed runtimes for Python, TypeScript, Go, Bash, SQL, and more.
• Performance & reliability: profiling, optimization, resource management. Our users run mission-critical workloads - correctness and uptime matter.
• Infrastructure: PostgreSQL schema design, caching, networking, deployment tooling.

Who we're looking for

This is a senior role. We're looking for someone who has operated distributed systems at scale and can teach us from day one - showing us PostgreSQL patterns, distributed systems techniques, and architectural improvements we haven't considered yet.

• Proven experience building and operating distributed systems at scale - not theoretical, you've done it in production
• Deep PostgreSQL expertise - query optimization, schema design, concurrency control, partitioning, replication. You know what breaks at scale and how to fix it.
• Strong systems programming skills - Rust experience strongly preferred, otherwise C/C++ with willingness to switch
• You bring opinions and techniques from previous infrastructure work that will make Windmill better immediately
• You enjoy hard infrastructure problems and care about correctness

Example projects in your first 3 months

• Redesign the job queue to handle bursty workloads with thousands of concurrent jobs without degrading scheduling latency
• Implement a new worker orchestration strategy that improves resource utilization across heterogeneous deployments (2 to 600 workers)
• Optimize critical PostgreSQL queries and schema for customers with millions of completed jobs - partitioning, indexing, vacuum tuning
• Add a new language runtime (e.g., Java, C#) with proper sandboxing, dependency management, and execution feedback
• Build observability tooling - distributed tracing across the flow execution engine to diagnose slow or failing steps in production

Offer details

Location: Paris hybrid (~3 days/week) or remote within France

Contract: CDI (permanent)

Salary: €60K–€90K gross + top of market for level + 20% bonus on collective milestones

About the interview

CV + a short note on what you've built and what you'd ship here → jobs@windmill.dev (subject: "Backend Engineer"). Bonus: link to a project, repo, or contribution.

1. Apply here or email jobs@windmill.dev
2. 30 min interview with founder
3. 1h case study with a team member
4. Paid trial project (can be evenings/weekends, ideally 20–80h)
5. You're hired

Play with the product and the codebase, and apply.

About Windmill

Windmill is an open-source developer platform (16k+ GitHub stars, Paris-based) that turns scripts into workflows, internal tools, and full-stack apps. It's the sweet spot between Retool and Temporal - we compete with both, plus Airflow and n8n, and we're winning on DX and performance.

How it works: write scripts in Python, TypeScript, Go, Bash, Rust, SQL, etc. Windmill analyzes their parameters and auto-generates UIs, turning each script into a standalone app or a reusable no-code module. Chain scripts into flows (branching, parallelism, retries, error handling) to build powerful workflows. Trigger anything via cron, webhook, auto-generated UI, or custom dashboards built with our app builder. Under the hood: an all-in-one queue/worker runtime, script editor, flow builder, secret manager, OAuth platform, with enterprise-grade permissions, groups, and audit logs.

The insight: no-code tools are intuitive but not extensible. Writing code is only 10% of the work - then you deal with credentials, CI/CD, permissions, UIs, error handling. Windmill handles all of that so developers focus on the logic that matters.

Stack: Rust / TypeScript + Svelte / PostgreSQL. Easy to deploy, works out of the box, replaces entire categories of internal infra.

Founded by Ruben Fiszel (ex-Palantir), who saw the need for enterprise workflow infrastructure but realized it had to be open-source, developer-focused, and built for best-in-class performance and DX - not another Spark wrapper.

300+ enterprise customers, 3M ARR, profitable. Tier 1 investors (YC, Google, Bessemer). Team of 10 engineers. Our customers run between 2 and 600 workers, 1 to +1,000 seats.

Revenue model: the core platform is fully open-source with thousands of individuals and companies using it for free. ~5% of features (enterprise-scoped: SSO, audit logs, dedicated workers, etc.) live in a private repository that companies pay to access, along with premium support. All revenue to date has been generated with zero outbound sales and modest marketing - purely inbound and product-led.