Backend Engineer - API
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Application is a CV plus a mandatory 'statement of exceptional work' — reviewed by engineers, not recruiters. Then a 15–30-minute phone screen with an engineer, and a main loop xAI's own job postings target to finish within ONE week: a coding assessment in your language of choice, two role-specific technical deep-dive sessions, and a 'Meet the Team' round where you present your exceptional work and your vision for xAI to a small audience. Coding is applied class design (key-value stores with transactions, LRU caches, iterators) that hardens via mid-problem extensions — completeness and bug-free code beat big-O talk — and design rounds demand working code in the same session. There is no dedicated behavioral or values round; decisions land within days with no hiring committee. Some loops run all-remote on Google Meet, others add an in-person Palo Alto onsite.
Read the full xAI interview process →Description
SpaceXAI’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 SpaceXAI 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)
COMPENSATION AND BENEFITS:
£107,000 - £262,000 GBP
Base salary is just one part of our total rewards package at SpaceXAI, which also includes equity, comprehensive healthcare and dental coverage, cash plan, income protection, life insurance, and various other discounts and perks.
SpaceXAI is an equal opportunity employer. For details on data processing, view our Recruitment Privacy Notice.