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

About The Role What if your C# expertise could directly shape the infrastructure powering next-generation AI? We're looking for a Senior C# Full-Stack Engineer to build and optimize the systems that leading AI labs depend on — from data pipelines and annotation tooling to evaluation infrastructure that influences how frontier models are trained and assessed. This is a fully remote contract role with meaningful technical challenges, real production impact, and the flexibility to work on your own terms. Organization: AlignerrType: Hourly ContractLocation: RemoteCommitment: 20–40 hours/week What You'll Do Design, build, and optimize high-performance C# systems supporting large-scale AI data pipelines and evaluation workflowsDevelop full-stack tooling and backend services for data annotation, validation, and quality control at scaleImprove reliability, performance, and safety across existing C# codebasesCollaborate with data, research, and engineering teams to support model training and evaluation workflowsIdentify bottlenecks and edge cases in data and system behavior, then implement scalable, production-ready fixesParticipate in synchronous design reviews to iterate on architecture and implementation decisions Who You Are Native or fluent English speaker with strong written and verbal communication skillsExperienced full-stack developer with a solid systems programming foundation3–5+ years of professional experience writing production C# code, with command of modern standardsDeep understanding of performance optimization, concurrency (threading, atomics), and memory safety (RAII, smart pointers, sanitizers)Able to commit 20–40 hours per week with reliability and consistencySelf-directed and comfortable working in fast-moving, async-first environments Nice to Have Prior experience with data annotation pipelines, data quality systems, or evaluation infrastructureFamiliarity with AI/ML workflows, model training loops, or benchmarking pipelinesExperience building distributed systems or developer tooling at scale Why Join Us Work directly with leading AI labs on systems that influence how frontier models are builtTackle genuinely hard engineering problems — not maintenance ticketsFully remote and flexible — structure your week around your best workFreelance autonomy with the substance of high-impact engineering workPotential for ongoing contracts and expanded scope as projects grow