Job Opportunities API

TLDR: We're looking for a Product Engineer (Backend – Rust) to own and evolve the core systems that power AI safety at scale – building APIs that handle hundreds of millions of requests, real-time policy enforcement, and high-throughput data pipelines. 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 • We 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 • Salary of $90,000 to $200,000 + equity • 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.