AI Engineer (Node.js / Next.js / Typescript)

TL;DR

AI Engineer (Node.js / Next.js / Typescript): Shaping AI infrastructure and driving production-ready LLM experiences with an accent on prompt systems, structured outputs, and complex LLM workflows. Focus on observability, debugging, and evaluation to continuously improve model quality and operational efficiency.

Location: Must be located within approximately ± 4 hours of CET (Central European Time)

Company

Ruby Labs is a leading tech company that creates and operates innovative consumer products across the health, education, and entertainment industries.

What you will do

• Design complex, dynamic prompt templates with conditional logic.
• Implement response schemes to ensure AI outputs are predictable.
• Build evaluation pipelines and using Langfuse to collect feedback and score the quality of responses in real time.
• Perform deep debugging of complex LLM chains using Langfuse traces to identify bottlenecks and optimize for cost, latency, and context window usage.
• Run systematic experiments across different models via OpenRouter and analyzing results based on quantitative metrics.
• Re-evaluate model performance as new architectures emerge and performing fine-tuning when necessary to meet specific domain requirements.

Requirements

• Deep knowledge of Node.js & Next.js to build reliable services and handle complex LLM-generated data.
• Proven experience in building prompts where content is highly dependent on input variables and context injection.
• Experience working with unified APIs, managing rate limits, and selecting the most cost-effective models for specific tasks.
• Understanding of LLM observability principles — setting up tracing, creating test datasets, and integrating scoring systems.
• Experience with frameworks like RAGAS or building custom “LLM-as-a-judge” systems.
• Applicants from any country are welcome to apply for the position as long as they are located within approximately ± 4 hours of CET.

Nice to have

• Practical experience in fine-tuning models for specific domain tasks or JSON compliance.
• Understanding how to build and optimize Retrieval-Augmented Generation systems, including indexing, retrieval, and re-ranking.
• Basic knowledge for working with data science scripts or AI evaluation libraries.

Culture & Benefits

• Embrace the freedom to work from anywhere, anytime, promoting a healthy work-life balance.
• Enjoy unlimited paid time off to recharge and prioritize your well-being, without counting days.
• Celebrate and relax on national holidays with paid time off to unwind and recharge.
• Experience seamless productivity with top-notch Apple MacBooks provided to all employees who need them.
• Unlock the benefits of flexibility, autonomy, and entrepreneurial opportunities with Flexible Independent Contractor Agreement.

Hiring process

• Recruiter Screening (40 minutes)
• Technical Interview (60 minutes)
• Final Interview (30 minutes)