About the Role

About Us

White Circle is an AI Safety company building the safety, reliability, and optimization layer for AI systems. At the core of our platform are policies – simple natural-language rules that define what an AI model should and shouldn’t do. We automatically test, enforce, and continuously improve these policies at scale.

We’ve raised $11M from top funds, founders, and senior leaders at OpenAI, Anthropic, HuggingFace, Mistral, DeepMind, Datadog, Sentry, and others.

We process over one hundred million API calls every month and fine-tune and train our own LLMs so they run faster and cheaper than any open or proprietary model. We’re a small, highly focused team. If you want to work deeply on hard problems, see your work ship to production quickly, and influence how AI safety is actually built – you’re the one we need.

You will:

Design and build backend services in Rust that handle real-time policy checks at scale – low latency, high reliability.
Own features end-to-end: from API design to database schema to deployment. You ship, you monitor, you iterate.
Work across the stack when needed – we care more about solving problems than role boundaries.
Improve system performance and reliability – connection pooling, caching strategies, query optimization, observability.
Collaborate directly with product, research to turn requirements into production systems.

You’ll fit right in if you:

You've built and shipped backend systems in Rust, Python or Go.
You're comfortable with async Rust (Tokio), web frameworks (Axum, Actix), and database access patterns.
You have strong fundamentals in system design – you can reason about trade-offs, failure modes, and scaling.
You've worked with PostgreSQL and know how to write efficient queries, design schemas, and debug performance issues.
You communicate clearly and work well with others. Fluent English.

A big plus:

Experience with ClickHouse, Redis, or Kafka/event streaming.
Experience with LLM infra, including LLM routing, inference systems, and RAG architectures.
Background in high-throughput monitoring systems, fintech.

Why White Circle

Meaningful equity package.
Paid time off in line with your local regulations, no matter where you work from.
Work from Paris (hybrid) + relocation package.
Best medical insurance in France.
All the hardware, tools, and services you need.
Covered subscriptions for AI agents and IDEs.
Team off-sites twice a year: we’ve recently been to the Alps and to Saint-Tropez.

How we hire

Intro call with one of our colleagues.
Show your best during the technical interview.
Final call with our CEO and Head of Engineering.

Please submit your application in English.

Requirements

Backend systems in Rust

You've built and shipped backend systems in Rust, Python or Go.

Async Rust and web frameworks

You're comfortable with async Rust (Tokio), web frameworks (Axum, Actix), and database access patterns.

System design fundamentals

You have strong fundamentals in system design – you can reason about trade-offs, failure modes, and scaling.

PostgreSQL experience

You've worked with PostgreSQL and know how to write efficient queries, design schemas, and debug performance issues.

Nice to Have

Experience with ClickHouse

Experience with ClickHouse, Redis, or Kafka/event streaming is a plus.

LLM infrastructure experience

Experience with LLM infra, including LLM routing, inference systems, and RAG architectures.

Monitoring systems background

A background in high-throughput monitoring systems, fintech is advantageous.

Benefits

Equity package

Meaningful equity package.

Paid time off

Paid time off in line with your local regulations, no matter where you work from.

Hybrid work

Work from Paris (hybrid) + relocation package.

Medical insurance

Best medical insurance in France.

Hardware and tools

All the hardware, tools, and services you need.

Subscriptions covered

Covered subscriptions for AI agents and IDEs.