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# Backend Engineers

- **Company:** Spacexsi
- **Location:** United Kingdom
- **Experience:** Expert
- **Salary:** £107,000 - £262,000
- **Contract:** Permanent contract
- **Skills:** Application Programming Interfaces (APIs), C++ (Programming Language), Databases, Data Normalization, Data Retention, Distributed Systems, PostgreSQL, MongoDB, Data Logging, Multi-Agent Systems, Backend, Containerization, Kubernetes, SGLang, Database Replication, TensorRT, Vertica, VLLM, Model Inference, Docker
- **Published:** November 7, 2026
- **Apply:** https://startup.jobs/sr-backend-engineer-api-xai-7944989

## About the Role

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., * 5+ years of experience in designing, implementing, and maintaining reliable and horizontally scalable distributed systems, * 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)

## Description

* 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