Senior Backend Engineer (C#) - AI Data Platform

* Design, build, and optimize high-performance C# systems supporting AI data pipelines and evaluation workflows * Develop backend services and full-stack tooling for large-scale data annotation, validation, and quality control * Improve reliability, performance, and safety across existing C# codebases * Collaborate with data, research, and engineering teams to support model training and evaluation * Identify bottlenecks and edge cases in data and system behavior — then implement scalable, production-ready fixes * Participate in synchronous design reviews to iterate on architecture and implementation decisions

Who You Are

* Native or fluent English speaker with clear written and verbal communication skills * 5+ years of professional experience building scalable backend services in C# * Strong systems programming background with full-stack development experience * Deep expertise in modern frameworks for building RESTful APIs and RPC services for inter-service communication * Experienced integrating with cloud-native data services and orchestrating workflows via message bus architectures * Able to commit 20–40 hours per week consistently

Nice to Have

* Prior experience with data annotation, data quality, or evaluation systems * Familiarity with AI/ML workflows, model training, or benchmarking pipelines * Experience with distributed systems or developer tooling

Why Join Us

* Work directly on cutting-edge AI infrastructure alongside leading research labs * Fully remote and flexible — work from wherever you do your best work * Freelance autonomy with the structure and impact of meaningful, high-stakes engineering * Contribute to systems that directly influence how next-generation AI models are built and evaluated * Potential for ongoing work and contract extension as new projects launch