Senior AI Engineer

About Us

Ruby Labs is a leading tech company focused on creating and operating innovative consumer products across the health, education, and entertainment sectors. We empower our innovative teams to shape the future of consumer-led products and are constantly seeking passionate individuals to join us. Discover our story at Ruby Labs About Us.

About the Role

We are seeking a Senior AI Engineer to lead the quality, reliability, and evolution of our AI systems in production. This is a high-ownership role where you will be responsible for the end-to-end delivery of major AI features, ensuring the production stability of AI systems, and conducting data-driven experimentation using tools like Langfuse, Mixpanel, and OpenRouter. You will work within a modern tech stack (Next.js, TypeScript, Node.js, Redis) and collaborate closely with product, growth, data, and billing teams. A key aspect of this role involves building agentic, tool-using AI systems, defining robust tool contracts, and orchestrating AI interactions with internal services and business systems. You will operate within an AI engineering squad, providing senior technical leadership and driving engineering quality.

Key Responsibilities

• End-to-End Delivery: Take complete ownership and deliver major AI engineering features within established timelines.
• AI Output Quality: Own and ensure the quality, structure, and predictability of AI outputs across all user-facing AI interactions.
• System Design: Design, implement, and maintain output-type-based AI systems, including segmentation, routing, and enforcement.
• LLM Consistency: Ensure consistent output structure and formatting across different LLMs for identical requests.
• LLM Integration: Integrate and orchestrate multiple LLM providers via OpenRouter, managing model selection, fallback strategies, and cost optimization.
• Agentic AI Workflows: Design and orchestrate tool-using and agentic AI workflows, defining clear tool contracts (including MCP-based tools), function-calling interfaces, and reliable AI-to-system integrations.
• Complex Workflows: Build and maintain multi-step LLM workflows, potentially using orchestration frameworks like LangChain or LlamaIndex, for advanced reasoning and retrieval.
• Prompt Management: Design and manage production prompt systems with dynamic prompting, context injection, and conditional logic.
• Experimentation & Evaluation: Own the deployment and release of LLM experiments, prompt management, and Langfuse-based evaluation pipelines.
• A/B Testing: Run A/B tests across models, analyze results, and present data-driven impact assessments.
• Monitoring & Observability: Monitor AI system metrics, quality signals, latency, and release health using Langfuse and other observability tools.
• Debugging & Optimization: Deep-debug complex LLM chains using Langfuse traces, identify bottlenecks, and optimize for cost, latency, and context-window usage. Build output-scoring systems to diagnose hallucinations and logic errors.
• Code Quality: Write clean, scalable, and maintainable TypeScript code within the Next.js and Node.js stack.
• Backend Reliability: Build robust backend logic for AI systems with strong error handling, request validation, fallback flows, and predictable production behavior.
• Engineering Standards: Ensure high code quality through testing, code reviews, and adherence to engineering standards.
• Performance & Reliability: Monitor, troubleshoot, and improve production performance, reliability, and system health.
• Maintainability: Drive maintainability and technical quality through solid architecture, refactoring, and disciplined release practices.

Qualifications

• Software Engineering Experience: 6+ years of backend/full-stack software engineering experience, including production-grade TypeScript/Node.js. Next.js and/or Python experience is a plus.
• AI/LLM Experience: 2+ years of experience building AI/LLM systems in production (exceptional candidates with less experience may be considered).
• LLM API Proficiency: Deep hands-on experience working with LLM APIs (OpenAI, Anthropic, or similar) in production.
• Agentic AI & RAG: Experience with Agentic AI, multi-agent orchestration, tool-based workflows (function calling/tool execution), and/or RAG pipelines.
• Observability Tools: Experience with LLM observability tools like Langfuse, LangSmith, or similar.
• AI Gateways: Experience with AI gateways and model routing solutions, such as OpenRouter or equivalent.
• Database Experience: Solid understanding of Redis and relational databases (e.g., PostgreSQL).
• Ownership Mindset: Exceptional ownership and personal responsibility for engineering quality and delivery.

Nice to Have

• Experience with AI-centered development tools (Cursor, Claude Code, etc.).
• Familiarity with evaluation frameworks (LLM-as-a-judge, RAGAS, etc.).
• Experience in high-pressure startup environments.
• Experience with MCP (Model Context Protocol).
• Experience with edge and serverless runtimes (Cloudflare Workers).
• Experience with payments, billing, or orchestration platforms.
• Practical experience fine-tuning models.
• Working proficiency in Python for data science or AI tooling.

Location

Ruby Labs operates within the CET (Central European Time) zone. Applicants located within approximately ± 4 hours of CET are encouraged to apply to ensure optimal collaboration.

Benefits

• Remote Work Environment: Enjoy the flexibility to work from anywhere, promoting work-life balance.
• Unlimited PTO: Take as much paid time off as you need to recharge.
• Paid National Holidays: Relax and celebrate national holidays with paid time off.
• Company-provided MacBook: Receive a top-tier Apple MacBook for seamless productivity.
• Flexible Independent Contractor Agreement: Benefit from autonomy, tax advantages, networking, and the freedom to work globally. Learn More

Join our fast-growing team and seize this excellent opportunity for personal and professional growth!