xAI· Engineering· London, UK
Backend Engineer - API
Classified Tasks (11)
Automate 0%Augment 73%Human-Only 27%
Augment (8)
AI assists, human decides
Build the xAI API that serves our models to developers worldwide
technical
Design and maintain model serving infrastructure for production inference
technical
Implement request routing for model inference traffic
technical
Develop and maintain SDKs for interacting with model serving APIs
technical
Implement and enforce rate limiting for API requests
technical
Implement and maintain observability, monitoring, and reliability practices for backend services
operational
Design and implement efficient scaling strategies to support billions of tokens per minute
technical
Contribute hands-on to building and maintaining backend infrastructure and production systems
technical
Human-Only (3)
Requires human judgment
Own and operate the end-to-end system responsible for high-throughput inference
operational
Ensure low-latency and high-availability operation of inference systems handling billions of tokens per minute
operational
Consciously and accurately share knowledge with teammates
communication
Job description
ABOUT xAI 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) xAI is an equal opportunity employer. For details on data processing, view our Recruitment Privacy Notice .