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

Alignerr Corp.; United States; Remote; MXN 1,406,000 - 2,174,000; Full time

Job summary

Alignerr Corp. is seeking a Senior C# Full-Stack Engineer to design, build, and optimize data pipelines, annotation tooling, and evaluation systems used by leading AI labs.

This remote hourly contract offers meaningful, production-grade work on real systems. You will collaborate with data, research, and infrastructure teams, tackle bottlenecks, and contribute to architecture reviews while committing to 20-40 hours per week.

Qualifications

• 3–5+ years of production C# experience.
• Strong full-stack capability with backend and tooling.
• Excellent written and spoken English.

Responsibilities

• Design, build, and optimize high-performance C# systems that power 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 production C# codebases
• Collaborate with data, research, and engineering teams to support model training and evaluation infrastructure
• 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

Skills

C# production

Full-stack development

Systems programming

Performance optimization

Concurrency

Memory safety

English communication

Job description

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 C# Full-Stack Engineer to build and optimize the data pipelines, annotation tooling, and evaluation systems that leading AI labs depend on every day.

This is a fully remote contract role working on real production systems - not toy projects. You'll be embedded in high-impact engineering workflows alongside data, research, and infrastructure teams pushing 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 C# systems that power 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 production C# codebases
• Collaborate with data, research, and engineering teams to support model training and evaluation infrastructure
• 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
• Experienced full-stack developer with a strong systems programming foundation
• 3-5+ years of professional experience writing production C# code, with familiarity in modern standards and best practices
• Strong background in performance optimization, concurrency (threading, atomics), and memory safety
• Able to commit 20-40 hours per week consistently
• Self-directed and comfortable working autonomously in a remote environment

Nice to Have

• Prior experience with data annotation, data quality pipelines, or evaluation systems
• Familiarity with AI/ML workflows, model training, or benchmarking infrastructure
• Experience with distributed systems or internal developer tooling
• Exposure to C++17/C++20 or other systems-level languages

Why Join Us

• Work directly with leading AI labs on production systems that shape next-generation models
• Fully remote and flexible - structure your work around your life
• Freelance autonomy with the depth and impact of meaningful, long-term technical work
• Contribute to AI infrastructure that has real, lasting consequences for how models are built and evaluated
• Potential for ongoing work and contract extension as new projects launch