Product Engineer (Backend)

Npv; Paris; Hybrid; EUR 71,000 - 133,000; Full time

Benefits offered by this job

Visa sponsorship

Relocation assistance

Equity

Job summary

White Circle is hiring a Product Engineer, Backend (Rust) to join our AI safety platform. You will design and build scalable Rust backend services that perform real-time policy checks and expose robust APIs.

You will own features end-to-end—from API design and schema to deployment and monitoring—while improving performance with connection pooling, caching, and observability. Relocation to Paris or London is supported for a hybrid work arrangement.

Qualifications

• Production experience with Rust, Python, or Go.
• Familiar with async Rust (Tokio), Axum or Actix, and PostgreSQL.
• Strong system design fundamentals including scaling and failure modes.
• Willing to relocate to Paris or London for hybrid work.

Responsibilities

• Design and build Rust backend services for real-time policy checks.
• Own features end-to-end: API design, schema, deployment, monitoring.
• Improve performance via caching, pooling, query optimization, and observability.
• Collaborate with product and research teams.

Skills

Rust

Python or Go

async Rust (Tokio)

Axum/Actix

PostgreSQL

Job description

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.

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.

Stack

• Rust, Tokio, Axum/Actix, PostgreSQL.
• Bonus: ClickHouse, Redis, Kafka, LLM infra (routing, inference, RAG), or high-throughput monitoring background.

We offer

• $80k–$150k/year salary + equity; 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

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