Backend C#/.NET Developer (Remote Contract)

About OpenTrain

OpenTrain is the #1 platform for finding and building careers in AI training and data labeling. We connect skilled contributors with projects that teach AI systems how to understand the world and behave responsibly.

Working through OpenTrain means joining a fast-growing, remote-friendly industry where you can build a durable freelance career by contributing real work that improves state-of-the-art AI.

About AI Training Work

AI training (also called data labeling or human feedback) is the human side of machine intelligence: people create, curate, and validate the examples models learn from. Backend systems that capture, process, and serve that data are essential to building reliable ML pipelines.

This role places you at the intersection of backend engineering and AI product development — your services and APIs will directly support data flows used for fine-tuning and evaluation of models.

The Role

OpenTrain is recruiting for a remote Backend C#/.NET Developer on contract to design, implement, and maintain backend services that help train next-generation AI systems. This is a part-time contract role with a minimum expectation of 20+ hours per week.

Pay is hourly between $30 and $55 USD. The position is fully remote and requires strong independent work habits and clear communication in English.

What You'll Do

You will own backend components and APIs that support data collection, processing, and model fine-tuning workflows. Typical work includes feature development, performance tuning, and production troubleshooting.

• Design, develop, and maintain robust backend services and RESTful APIs using C# and .NET frameworks.
• Collaborate with cross-functional teams to define technical requirements and deliver scalable solutions.
• Optimize backend processes for performance, scalability, and maintainability.
• Troubleshoot, debug, and resolve issues in staging and production environments.
• Document architecture, technical specifications, and operational runbooks for team use.
• Contribute to continuous improvement of development processes and best practices.

Requirements

All requirements below come from the role description. Candidates must be able to work remotely and manage priorities for a part-time contract engagement.

• Expert-level proficiency in C# and the .NET ecosystem.
• Strong experience with MySQL, including schema design and query optimization.
• Solid understanding of server-side logic, RESTful API development, and integration patterns.
• Track record of writing clean, maintainable, and well-documented code.
• Excellent written and verbal communication skills in English.
• Ability to work independently in a fully remote setting and manage priorities effectively.
• Proactive problem-solving skills and a commitment to continuous learning.

Helpful Background

The following experiences are listed as helpful but not strictly required in the posting. They indicate the engineering environment and practices OpenTrain values.

• Experience developing and deploying cloud-hosted applications on AWS, Azure, or GCP.
• Experience working with distributed teams and Agile methodologies.
• Previous work in high-growth, innovation-driven environments.

How To Apply & What To Expect

If this role fits your skills, apply through OpenTrain to submit your profile and relevant experience. Be sure to highlight C#/.NET projects, MySQL work, and any cloud deployments.

Selected candidates will participate in technical screening and may be asked to review or explain code samples and backend architecture decisions. This is a contract, part-time engagement paid hourly at $30–$55 USD.

• Time expectation: 20+ hours per week (part-time contractor).
• Language: English proficiency required.
• Employment types: Contractor, Part-time; fully remote.