Backend Engineer - API

SpaceXSI; Greater London; On-site; GBP 110,000 - 150,000; Full time

Benefits offered by this job

Equity

Healthcare and dental coverage

Cash plan

Income protection

Life insurance

Job summary

SpaceXSI is seeking a backend engineer to build and operate scalable production infrastructure for model serving. You will work primarily with Rust or C++, focusing on high-throughput inference, low latency, and reliability across distributed systems. Familiarity with Docker, Kubernetes, and gRPC will be highly beneficial.

You will own end-to-end responsibilities from API design to observability and scaling, ensuring robust deployment of billions of tokens per minute for developers worldwide.

Qualifications

• Expert knowledge of either Rust or C++.
• 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 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.

Skills

Rust

C++

Distributed systems

Observability

Tools

Docker

Kubernetes

gRPC

PostgreSQL

ClickHouse

MongoDB

Job description

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.

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 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

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:

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.