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

About The RoleWhat 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: AlignerrType: Hourly ContractLocation: RemoteCommitment: 20–40 hours/weekWhat You'll DoDesign, build, and optimize high-performance C# systems that support AI data pipelines and evaluation workflowsDevelop full-stack tooling and backend services for large-scale data annotation, validation, and quality controlImprove reliability, performance, and safety across existing C# codebases used in production AI environmentsCollaborate closely 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, robust fixesParticipate in synchronous design reviews to iterate on architecture and implementation decisionsWho You AreFull-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 standardsSolid grounding in performance optimization, concurrency (threading, atomics), and memory safetyNative or fluent English speaker with clear written and verbal communication skillsSelf-directed and reliable — able to commit 20–40 hours per week and deliver consistently without hand-holdingComfortable navigating complex codebases and making principled architectural decisions under real constraintsNice to HavePrior experience with data annotation platforms, data quality systems, or evaluation infrastructureFamiliarity with AI/ML workflows, model training pipelines, or benchmarking systemsExperience building distributed systems or developer tooling at scaleBackground working alongside research or applied AI teamsWhy Join UsWork at the frontier of AI — your code will directly influence how the world's leading models are built and evaluatedFully remote and flexible — structure your hours around your life, not the other way aroundCollaborate with world-class research and engineering teams on genuinely hard problemsFreelance autonomy with the substance of high-impact, technically demanding workPotential for ongoing work and contract extension as projects evolve and expand