Backend Engineer - API

xAI; Greater London; On-site; GBP 60,000 - 80,000; Full time

Job summary

xAI is seeking a skilled software engineer to build their API that serves AI models to developers globally. The ideal candidate will have expert knowledge of Rust or C++, experience in designing reliable distributed systems, and familiarity with databases like PostgreSQL and MongoDB. The role entails owning the entire system for high-throughput inference and contributing to innovative AI solutions within a motivated team. xAI values communication and initiative, offering a flat structure and opportunities for personal growth.

Qualifications

• Expert knowledge of either Rust or C++.
• Experience in designing, implementing, and maintaining reliable and horizontally scalable distributed systems.
• Knowledge of service observability and reliability best practices.
• Experience in operating commonly used databases such as PostgreSQL, Clickhouse, and MongoDB.

Responsibilities

• Build the xAI API that serves models to developers worldwide.
• Own the end-to-end system responsible for high-throughput inference.

Job description

xAI’s mission is to create AI systems that can accurately understand the universe and aid humanity in its pursuit of knowledge. Our team is small, highly motivated, and focused on engineering excellence. This organization is for individuals who appreciate challenging themselves and thrive on curiosity. We operate with a flat organizational structure. All employees are expected to be hands‑on and to contribute directly to the company’s mission. Leadership is given to those who show initiative and consistently deliver excellence. Work ethic and strong prioritization skills are important. All employees are expected to have strong communication skills. They should be able to concisely and accurately share knowledge with their teammates.

About the role

As an ideal candidate you have a good understanding of how highly scalable and reliable production infrastructure is built. Most of our backend infrastructure is written in Rust. So familiarity with a compiled language such as C++, Rust, or Go is highly beneficial.

Responsibilities

• Build the xAI API that serves our models to developers worldwide
• Own the end-to-end system responsible for high-throughput inference, handling billions of tokens per minute with low latency and high availability, including model serving infrastructure, request routing, SDK development, rate limiting, observability, and efficient scaling

Basic Qualifications

• Expert knowledge of either Rust or C++
• Experience in designing, implementing, and maintaining reliable and horizontally scalable distributed systems
• Knowledge of service observability and reliability best practices
• Experience in operating commonly used databases such as PostgreSQL, Clickhouse, and MongoDB

Preferred Skills and Experience

• Experience with LLM inference engines and serving frameworks (e.g., SGLang, TensorRT, vLLM)
• Experience designing or building with agent SDKs and agent orchestration frameworks
• Experience with Docker, Kubernetes, and containerized applications
• Expert knowledge of gRPC (unary, response streaming, bi-directional streaming, REST mapping)

Equal Opportunity

xAI is an equal opportunity employer. For details on data processing, view our Recruitment Privacy Notice.