Intermediate Fullstack Engineer (Ruby/Vue.js), AI Engineering, Custom Models

GitLab is an open-core software company that develops the most comprehensive AI-powered DevSecOps Platform, used by more than 100,000 organizations. Our mission is to enable everyone to contribute to and co-create the software that powers our world. When everyone can contribute, consumers become contributors, significantly accelerating human progress. Our platform unites teams and organizations, breaking down barriers and redefining what's possible in software development. Thanks to products like Duo Enterprise and Duo Agent Platform, customers get AI benefits at every stage of the SDLC. The same principles built into our products are reflected in how our team works: we embrace AI as a core productivity multiplier, with all team members expected to incorporate AI into their daily workflows to drive efficiency, innovation, and impact. GitLab is where careers accelerate, innovation flourishes, and every voice is valued. Our high-performance culture is driven by our values and continuous knowledge exchange, enabling our team members to reach their full potential while collaborating with industry leaders to solve complex problems. Co-create the future with us as we build technology that transforms how the world develops software.

An Overview of This Role

The Custom Models team is responsible for Duo Self-Hosted, a key component in GitLab AI that allows customers to run GitLab Duo features in completely private environments, connecting GitLab to their own AI models. The team works collaboratively with numerous teams to ensure a complete lifecycle of features that implement controls for customization and guarantee a smooth experience for our largest customers. In the near future, the team will return to evaluating LLM models and advancing AI capabilities.

What You’ll Do

• Contribute to our features using JavaScript (30%), Ruby on Rails (50%), and Python (20%), working with both frontend and backend components in a mature codebase.
• Collaborate closely with backend, frontend, product, and UX teammates across time zones in an async-first environment.
• Write maintainable, well-tested code and participate in code reviews that help you and your team grow.
• Maintain and improve the quality and stability of our applications by contributing to bug fixes and QA.
• Resolve production issues, supporting customers and resolve production issues, and learning along the way.
• Operate in an agile and fast-paced environment, adapt to shifting priorities and project types, and focus on outcomes.
• Take ownership of projects from proposal to production, collaborating across teams to deliver end-to-end solutions.

What You’ll Bring

• Full-stack development experience: Proven ability to work across the stack, with experience distributed approximately across JavaScript (30%), Ruby (50%), and Python (20%). Comfortable working with both frontend and backend components in a mature codebase.
• Strong JavaScript skills: Experience with modern JavaScript (and ideally a framework like Vue.js), particularly in the context of full-stack development.
• Strong Ruby and Python skills: Experience building and maintaining production applications using Ruby on Rails and Python, including work with background jobs, APIs, and data models.
• API development: Experience designing or extending REST and/or GraphQL APIs with attention to scalability, maintainability, and backward compatibility.
• LLM prompting and integrations: Hands-on experience with prompt engineering, integrating LLMs into applications, and building features powered by generative AI.
• SQL and data layer expertise: Strong command of writing efficient queries and working with relational databases such as PostgreSQL.
• Performance-minded: Skilled at identifying and resolving performance bottlenecks at both application and infrastructure levels.

Nice-to-Haves

• Familiarity with LLM evaluation, RAG patterns, or ML model deployment (especially using cloud platforms like AWS or GCP).
• Experience with Langchain, LangSmith, DSpy, or similar LLM/AI frameworks.
• Contributions to open-source projects (especially GitLab or ML-related).

Why Join Us

This isn't just a job; it's your chance to shape the future of AI at GitLab. You will be working on one of the most impactful products at GitLab. We operate asynchronously, with a strong environment of support, ownership, and collective success. You'll gain deep expertise in Ruby, Python, and the GitLab platform while contributing to a core area of the product that directly supports millions of users.

As part of our team, you’ll:

• Work on a widely-used open core product with passionate contributors and users
• Grow in a high-trust environment that values transparency and iteration
• Collaborate closely with Product and UX partners
• Have access to a defined career development framework and opportunities for mentorship and growth

About the Team

The Custom Models team consists of GitLab team members from around the globe. Engineers are primarily located across various European countries, with some members in Australia and Canada.

The team works closely with these other teams within the organization:

• AI Framework
• MLOps
• Model Validation
• Duo Chat

How GitLab Will Support You

• Benefits to support your health, finances, and well-being
• All remote, asynchronous work environment
• Flexible Paid Time Off
• Team Member Resource Groups
• Equity Compensation & Employee Stock Purchase Plan
• Growth and development budget
• Parental leave
• Home office support

Please note that we welcome interest from candidates with varying levels of experience; many successful candidates do not meet every single requirement. Additionally, studies have shown that people from underrepresented groups are less likely to apply to a job unless they meet every single qualification. If you're excited about this role, please apply and allow our recruiters to assess your application.

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