Sr. Backend Engineer, API

SR. BACKEND ENGINEER, API

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:

• Build and maintain the unified inference stack as the single surface area for all inference needs across the company
• Own and evolve the platform services that power Chat API, Imagine API, Voice API, Grok Build, and Grok Bot
• Design, build, and maintain Chat API features including batch API, collections API, files API, and related capabilities
• Implement and operate chat moderation and abuse protection systems across the API and grok.com
• Build and maintain the company-wide logging system for all request types, including enforcement of Zero Data Retention (ZDR) policies
• Manage multi-region inference cluster (IC) deployments, data aggregation, data replication, and the distributed authentication system
• Participate in follow-the-sun on-call coverage (UK → Japan → US) to ensure continuous reliability of the inference platform

BASIC QUALIFICATIONS:

• 5+ years of experience in designing, implementing, and maintaining reliable and horizontally scalable distributed systems
• Experience with Rust or C++

PREFERRED SKILLS AND EXPERIENCE:

• Experience in operating databases such as PostgreSQL, Clickhouse, and MongoDB
• 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)

COMPENSATION AND BENEFITS:

£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.