Member of Technical Staff — Backend/API Platform

About the Role 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. Requirements

• 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

Responsibilities

• 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

About RadixArk 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. Compensation Depending on background, skills, and experience, the expected annual salary range for this position is $200,000 - $400,000 USD + equity. Equal Opportunity RadixArk is an Equal Opportunity Employer and is proud to offer equal employment opportunity to everyone regardless of race, color, ancestry, religion, sex, national origin, sexual orientation, age, citizenship, marital status, disability, gender identity, veteran status, and more.