Product Engineer (Backend)

We're looking for a Product Engineer, Backend (Rust) to join White Circle , an AI Safety company building the safety, reliability, and optimization layer for AI systems through natural-language policies it automatically tests, enforces, and improves at scale. Backed by $70M (Series A) from top funds and senior leaders at OpenAI, Anthropic, HuggingFace, Mistral, DeepMind, and others, White Circle processes 100M+ API calls monthly and fine-tunes and trains its own LLMs to run faster and cheaper than open or proprietary models. Responsibilities You will Design and build Rust backend services handling real-time policy checks at scale. Own features end-to-end - API design, schema, deployment, monitoring. Improve performance and reliability through connection pooling, caching, query optimization, and observability. Collaborate directly with product and research. Requirements Production experience with Rust, Python, or Go. Comfortable with async Rust (Tokio), Axum/Actix, and PostgreSQL - schema design, query optimization, debugging. Strong system design fundamentals: trade-offs, failure modes, scaling. Relocation to Paris or London (hybrid) required. Bonus ClickHouse, Redis, Kafka, LLM infra (routing, inference, RAG), or high-throughput monitoring background. Benefits higher figures can be negotiated. Official employment, visa and relocation help. Compensation: $80K - $150K - Higher figures and equity are negotiable - $80K - $150K - Higher figures and equity are negotiable #J-18808-Ljbffr