Senior Backend Engineer (C#) - AI Data Platform

Seattle

**Senior Backend Engineer (C#) --- AI Data Platform** **About The Role** What if your C# expertise could directly shape the infrastructure powering the next generation of AI? We're looking for a Senior Backend Engineer to design and build the high-performance data pipelines, annotation tooling, and evaluation systems that leading AI labs depend on to train and improve their models. This is a fully remote contract role with flexible hours. You'll be working on real production systems --- not toy projects --- alongside data, research, and engineering teams at the frontier of AI development. * Organization: Alignerr * Type: Hourly Contract * Location: Remote * Commitment: 20--40 hours/week **What You'll Do** * Design, build, and optimize high-performance backend systems in C# supporting large-scale AI data pipelines and evaluation workflows * Develop backend services and tooling for data annotation, validation, and quality control at scale * Build and maintain RESTful APIs and RPC services for reliable inter-service communication * Integrate with cloud-native data services and orchestrate workflows via message bus architectures * Identify bottlenecks, edge cases, and reliability issues across existing codebases --- then implement scalable fixes * Collaborate with research and engineering teams to support model training, benchmarking, and evaluation workflows * Participate in synchronous design reviews and iterate on system architecture decisions **Who You Are** * 5+ years of professional experience building scalable backend services in C# * Deep command of modern C# frameworks for RESTful APIs and RPC-based inter-service communication * Experienced integrating with cloud-native data services and message bus architectures * Systems-level thinker who can identify performance issues and architect clean, scalable solutions * Clear, concise written and verbal communicator --- comfortable working with cross-functional teams * Native or fluent English speaker * Able to commit 20--40 hours per week consistently **Nice to Have** * Prior experience with data annotation platforms, data quality systems, or evaluation pipelines * Familiarity with AI/ML workflows, model training, or benchmarking infrastructure * Experience with distributed systems design or developer tooling * Full-stack background with frontend exposure alongside a strong backend foundation **Why Join Us** * Work directly on cutting-edge AI projects alongside leading research labs * Fully remote and flexible --- work from wherever you do your best work * Freelance autonomy with the structure of meaningful, high-impact engineering work * Contribute to infrastructure that shapes how next-generation AI systems are built and evaluated * Potential for ongoing work and contract extension as new projects launch