Member of Technical Staff - Backend/API Platform

RadixArk is looking for a Member of Technical Staff - Backend/API Platform Engineer to build the API layer, control plane, and platform services that power SGLang and Miles in production. You’ll design and implement the REST/gRPC APIs, authentication systems, multi-tenancy isolation, and monitoring infrastructure that thousands of developers and companies rely on. This role bridges high-performance inference/training systems with production-grade platform engineering., * Design and build production APIs for SGLang and Miles: REST/gRPC endpoints, client SDKs, API versioning

• Implement authentication, authorization, and rate limiting systems for multi-tenant deployments
• Build control plane infrastructure: job scheduling, resource allocation, model deployment management
• Create monitoring, logging, and observability systems for production inference and training workloads
• Design and implement billing integration, usage tracking, and quota management
• Build management dashboards and admin tools for cluster operations
• Ensure API reliability, performance, and security at scale
• Implement multi-tenancy isolation and security boundaries
• Create deployment automation, CI/CD pipelines, and rollback procedures
• Write comprehensive API documentation and integration guides
• Partner with Systems Engineers to optimize end-to-end latency from API serving layer
• Debug production issues and implement reliability improvements

Application Programming Interface (API), Authentication, Application Programming Interface (API), REST (Representational State Transfer), Production Systems, Computer Science, Python Programming/Scripting Language, Go Programming Language (Golang), Quality Metrics, Distributed Computing, * 4+ years experience building production backend systems, APIs, or platform infrastructure

• Bachelor’s or Master’s degree in Computer Science, Engineering, or equivalent industry experience
• Strong proficiency in Python, Go, or Rust with production-quality code standards
• Experience designing and building REST/gRPC APIs at scale
• Solid understanding of distributed systems, databases, caching, and message queues
• Experience with authentication, authorization, rate limiting, and multi-tenancy
• Familiarity with cloud platforms (AWS, GCP, Azure) and Kubernetes
• Experience with monitoring and observability tools (Prometheus, Grafana, DataDog)
• Understanding of ML serving infrastructure or high-throughput systems is a plus

Depending on background, skills, and experience, the expected annual salary range for this position is $200,000 - $400,000 USD + equity.

RadixArk is an infrastructure-first company built by engineers who’ve shipped production AI systems, created SGLang (30K+ GitHub stars, the fastest open LLM serving engine), and developed Miles (our large-scale RL framework). Founded by AI infrastructure veterans from xAI and NVIDIA, we’re on a mission to democratize frontier-level AI infrastructure by building world-class open systems for inference and training. Our team has optimized kernels serving billions of tokens daily, designed distributed training systems coordinating 10,000+ GPUs, and contributed to infrastructure that powers leading AI companies and research labs.