Java Backend Engineer — AI Training

About OpenTrain

OpenTrain is the #1 platform for finding and building careers in AI training and data labeling. We help people start and grow careers teaching AI by consolidating opportunities, building unified portfolios, and providing a single place to apply and work.

For this role, OpenTrain is the hiring and contracting organization. Creating an OpenTrain account is free and gives you access to projects, a profile that showcases your experience, and tools to manage contract work.

Why AI Training Work Matters

AI training (also called data labeling or human feedback work) is the human side of building modern AI systems—people prepare, review, and improve the examples models learn from. That work powers everything from chatbots to search and recommendation systems.

This role gives you direct technical influence on real-world AI systems by contributing backend software that supports data pipelines, annotation tooling, model evaluation workflows, and reliable service infrastructure.

The Role

OpenTrain is hiring a Java AI Training Developer to support AI system training through expert backend engineering. This hands-on, technical role focuses on designing, developing, and maintaining scalable Java and Spring Boot systems that help training workflows run reliably.

You will work as a part-time contractor (20+ hours/week) and contribute practical, production-quality backend work—building microservices, improving performance and reliability, reviewing technical specs, and producing clear documentation and code review feedback.

What You'll Do

• Build and maintain backend systems using Java and Spring Boot.
• Architect and implement microservices for complex application needs.
• Review technical specifications and collaborate on code quality improvements.
• Improve application performance, reliability, and security.
• Troubleshoot, debug, and optimize backend systems and APIs.
• Document processes, design decisions, and solutions clearly for teammates.

Requirements

This position requires strong hands-on expertise in Java backend development and Spring Boot, plus experience designing microservices and producing maintainable code. Strong written and verbal communication is mandatory for clear documentation and constructive code reviews.

• Expert Java programming ability and proven backend development experience.
• Hands-on Spring Boot experience and familiarity with REST APIs and backend best practices.
• Strong understanding of microservices architecture and data structures.
• Ability to write clean, maintainable, efficient code and constructive code review feedback.
• Solid written documentation skills and clear verbal communication.

Helpful Background

The following are helpful but not strictly required: exposure to cloud platforms (AWS, Azure, or Google Cloud), experience with AI-driven or data-intensive projects, and background in distributed or high-availability systems.

• Cloud platform experience (AWS, Azure, or GCP).
• Experience on AI-driven, data-intensive, or distributed systems.
• Previous work on high-availability or performance-critical backends.

Compensation, Schedule, and How to Apply

This is a contract, part-time role for 20+ hours per week. Pay is hourly in USD; the project lists rates up to $90/hr (hourly range $30–$90). The role is open worldwide and conducted in English.

To apply, create a free OpenTrain account and submit your application for this role. Include a brief summary of your Java and Spring experience and, if available, links to code samples or documentation that demonstrate your backend work.

• Employment type: Contractor, Part-time.
• Time commitment: 20+ hours/week.
• Pay: Hourly, USD, up to $90/hour (range $30–$90).
• Language: English. Remote, worldwide.