Backend Engineer, API

United Kingdom·Londonmid

EngineeringBackend Developer

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Quick Summary

Overview

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.

Key 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…

Technical Tools

cppdockergokubernetesmongodbpostgresqlrustdistributed-systems

SpaceX was founded under the belief that a future where humanity is out exploring the stars is fundamentally more exciting than one where we are not. Today, SpaceX is actively developing the technologies to make this possible, with the ultimate goal of making life multiplanetary and expanding consciousness to the stars.

SpaceXSI is building Super Intelligence to help humanity understand the universe. Our teams are building the full Super Intelligence stack: from our Colossus supercomputers, to Grok models, to our suite of applications, including Grok Bot, Grok Build, Grok Imagine, Grok Voice, and X. We're creating a powerful flywheel where more compute trains better models, better models power more useful products, and what we learn from people using those products shapes what we build next.

We are looking for Backend Engineers to help build and operate highly scalable, reliable production infrastructure. Most of our backend infrastructure is written in Rust. Experience with a compiled language such as Rust, C++, or Go is highly beneficial.

Responsibilities

~1 min read

→Build the SpaceXSI 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

Requirements

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Experience with Rust or C++
Experience in operating databases such as PostgreSQL, Clickhouse, and MongoDB

Experience in designing, implementing, and maintaining reliable and horizontally scalable distributed systems
Knowledge of service observability and reliability best practices
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)

What We Offer

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£107,000 - £262,000 GBP

Base salary is just one part of our total rewards package at SpaceXSI, which also includes equity, comprehensive healthcare and dental coverage, cash plan, income protection, life insurance, and various other discounts and perks.

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