Senior C# Full-Stack Engineer — AI Data & Infrastructure

Denver

**About The Role** What if your C# expertise could directly shape the infrastructure powering the world's most advanced AI systems? We're looking for a Senior C# Full-Stack Engineer to build and optimize the data pipelines, annotation tooling, and evaluation systems that leading AI labs depend on to train and improve next-generation models. This is a fully remote, flexible contract role for an experienced engineer who wants to work on real production systems at the frontier of AI --- not just maintain legacy code, but architect meaningful infrastructure that matters. * Organization: Alignerr * Type: Hourly Contract * Location: Remote * Commitment: 20--40 hours/week **What You'll Do** * Design, build, and optimize high-performance C# systems that support AI data pipelines and evaluation workflows * Develop full-stack tooling and backend services for large-scale data annotation, validation, and quality control * Improve reliability, performance, and safety across existing C# codebases used in production AI environments * Collaborate closely with data, research, and engineering teams to support model training and evaluation workflows * Identify bottlenecks and edge cases in data and system behavior --- then implement scalable, robust fixes * Participate in synchronous design reviews to iterate on architecture and implementation decisions **Who You Are** * Full-stack developer with a strong systems programming background and deep command of C# * 3--5+ years of professional experience writing production-grade C# code, with familiarity with modern standards * Solid grounding in performance optimization, concurrency (threading, atomics), and memory safety * Native or fluent English speaker with clear written and verbal communication skills * Self-directed and reliable --- able to commit 20--40 hours per week and deliver consistently without hand-holding * Comfortable navigating complex codebases and making principled architectural decisions under real constraints **Nice to Have** * Prior experience with data annotation platforms, data quality systems, or evaluation infrastructure * Familiarity with AI/ML workflows, model training pipelines, or benchmarking systems * Experience building distributed systems or developer tooling at scale * Background working alongside research or applied AI teams **Why Join Us** * Work at the frontier of AI --- your code will directly influence how the world's leading models are built and evaluated * Fully remote and flexible --- structure your hours around your life, not the other way around * Collaborate with world-class research and engineering teams on genuinely hard problems * Freelance autonomy with the substance of high-impact, technically demanding work * Potential for ongoing work and contract extension as projects evolve and expand