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

Alignerr; Brasil; Remote; BRL 453,000 - 905,000; Full time

Job summary

Alignerr is seeking a Senior C# Full-Stack Engineer to design and optimize data pipelines, annotation tooling, and evaluation systems used by leading AI labs. This is a high-impact, fully remote hourly contract for an experienced engineer who thrives on solving hard systems problems and delivering at scale.

You will build high-performance C# systems, backend services for large-scale data annotation, validation, and quality control, and collaborate with data, research, and engineering teams to

Qualifications

• 3–5+ years of production-grade C# development experience.

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 of existing C# codebases used in production AI research environments.
• Collaborate 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, production-ready fixes.
• Participate in design reviews to iterate on architecture and implementation decisions with engineers.

Skills

C#

Full-stack

Performance

Concurrency

Tools

ASP.NET

Entity Framework

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 to train and improve their models.

This is a high-impact, fully remote contract role for an experienced engineer who thrives on solving hard systems problems and wants their work to matter at scale.

• 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 the reliability, performance, and safety of existing C# codebases used in production AI research environments
• Collaborate 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, production-ready fixes
• Participate in synchronous design reviews to iterate on architecture and implementation decisions with top engineering talent

Who You Are

• Full-stack developer with a strong systems programming background and deep C# expertise
• 3–5+ years of professional experience writing production-grade C# code, with fluency in modern standards
• Solid understanding of 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 without hand-holding
• Comfortable working asynchronously across distributed teams

Nice to Have

• Prior experience with data annotation pipelines, data quality systems, or evaluation infrastructure
• Familiarity with AI/ML workflows, model training, or benchmarking systems
• Experience with distributed systems architecture or developer tooling
• Background working with or alongside AI research teams

Why Join Us

• Work on real, production systems used by leading AI labs — not toy projects
• Fully remote and flexible — work from wherever you do your best work
• Freelance autonomy with the structure of meaningful, high-stakes engineering work
• Collaborate with world-class researchers and engineers on problems that matter
• Potential for ongoing work and contract extension as projects evolve and expand