Senior Full Stack Engineer (Remote, Contract)

About OpenTrain

OpenTrain is the #1 platform for people starting and growing careers in AI training and data labeling. We help technical and nontechnical contributors discover projects, build a unified AI-training portfolio, and turn short-term gigs into durable freelance careers.

We hire engineers directly to build the tools and infrastructure that make high-quality AI training possible — from annotation platforms to APIs that deliver labeled data to models in production.

About AI training work

AI training (also called data labeling or annotation) is the human side of building modern AI. Engineers on our team create reliable, scalable software used daily by contributors who prepare and review training data for models.

Working here means your code directly improves data quality and the workflow of hundreds or thousands of annotators, helping shape how state-of-the-art models behave.

The role

We are hiring a Senior Full Stack Engineer to design, develop, test, and maintain robust web applications that support AI-training operations. You will contribute across backend and frontend systems, optimize for speed and scalability, troubleshoot production issues, participate in architecture and code reviews, and mentor teammates.

Strong written and verbal communication is essential: you will explain technical tradeoffs clearly to engineers and nontechnical stakeholders and produce maintainable, well-documented code.

What you'll do

You will own features and components end-to-end across the stack, work independently on delivery while collaborating with a distributed team, and contribute engineering input that makes annotation workflows more reliable and efficient.

• Build and maintain web applications using NodeJS, TypeScript, Python, JavaScript, and Java.
• Develop and consume RESTful APIs to support annotation workflows and integrations.
• Optimize applications for performance, scalability, and maintainability.
• Participate in code reviews, architecture discussions, debugging, and incident resolution.
• Mentor junior engineers and communicate technical designs in clear written and verbal form.
• Contribute engineering work that supports high-quality AI training and code-labeling tasks.

Required skills & experience

The role requires practical full-stack experience and strong software development fundamentals. We will evaluate your ability to deliver production-quality systems and communicate technical work clearly.

• 3+ years of full-stack development experience.
• Strong experience with NodeJS, TypeScript, Python, JavaScript, and Java.
• Proven ability to build and consume RESTful APIs.
• Experience with Git and software development best practices.
• Familiarity with Agile methodologies and working in distributed teams.
• Excellent written and verbal communication and attention to detail.

Helpful background

These are nice-to-have skills that help you ramp faster, but are not strictly required.

• Familiarity with cloud platforms such as AWS, Azure, or GCP.
• Experience with microservices, containerization, and CI/CD.
• Prior experience collaborating with global teams and cross-functional stakeholders.