ruby-labs - AI Engineer
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Requirements
• 6+ years of backend/full-stack software engineering experience, including production-grade TypeScript/Node.js. Experience with Next.js and/or Python is a plus. • 2+ years of experience building AI/LLM systems in production. Less experience may be considered for exceptional candidates. • Deep hands-on experience working with LLM APIs (OpenAI, Anthropic, or similar) in production environments. • Experience with Agentic AI, multi-agent orchestration, tool-based workflows (function calling/tool execution), and/or RAG pipelines, including indexing, retrieval, and re-ranking. • Experience with LLM observability tools such as Langfuse, LangSmith, or similar platforms. • Experience with AI gateways and model routing solutions, such as OpenRouter or equivalent technologies. • Solid understanding of Redis and relational databases, such as PostgreSQL. • Exceptional ownership mindset and personal responsibility for engineering quality and delivery. • Experience with AI-centered development tools such as Cursor, Claude Code, Windsurf, or similar platforms. • Familiarity with evaluation frameworks, including LLM-as-a-judge, RAGAS, or similar approaches. • Experience working in high-pressure startup environments with rapid product iteration cycles. • Experience with MCP (Model Context Protocol), including building MCP servers/clients or designing tool contracts for AI agents. • Experience with edge and serverless runtimes, such as Cloudflare Workers, and supporting services including KV, Durable Objects, Queues, R2, and D1. • Experience with payments, billing and checkout flows, or orchestration platforms. • Practical experience fine-tuning models for domain-specific tasks or achieving strict JSON/schema compliance. • Working proficiency in Python for data science, evaluation scripts, or AI tooling. • Ruby Labs operates within the CET (Central European Time) zone. Applicants from any country are welcome to apply for the position as long as they are located within approximately ± 4 hours of CET. This ensures optimal collaboration and communication during working hours.
Responsibilities
• Take complete ownership and deliver major AI engineering features within agreed timelines. • Own AI output quality, structure, and predictability across all user-facing AI interactions. • Design, implement, and maintain output-type-based AI systems, including segmentation, routing, and enforcement. • Ensure consistent output structure and formatting across different LLMs for the same request type. • Integrate and orchestrate multiple LLM providers via OpenRouter, managing model selection, fallback strategies, and cost optimisations. • Design and orchestrate tool-using and agentic AI workflows, defining clean tool contracts (including MCP-based tools), function-calling interfaces, and reliable AI-to-system integrations. • Build and maintain complex, multi-step LLM workflows, including with orchestration frameworks such as LangChain or LlamaIndex, for advanced reasoning, context reuse, and retrieval. • Design and manage production prompt systems with dynamic prompting, context injection, and conditional logic. • Own the deployment and release of LLM experiments, prompt management, and Langfuse-based evaluation pipelines. • Run A/B tests across models, analyse results, and present data-driven impact assessments of AI features and experiments. • Monitor AI system metrics, quality signals, latency, and release health using Langfuse and other observability tools. • Deep-debug complex LLM chains using Langfuse traces, identifying bottlenecks and optimising for cost, latency, and context-window usage, and build output-scoring systems to root-cause hallucinations and logic errors. • Write clean, scalable, and maintainable TypeScript code across the Next.js and Node.js stack. • Build reliable backend logic for AI systems, with strong error handling, request validation, fallback flows, and predictable behaviour in production, including reliable tool execution and AI-to-service integrations. • Ensure high code quality through testing, code reviews, and clear engineering standards. • Monitor, troubleshoot, and improve production performance, reliability, and system health. • Drive maintainability and technical quality through solid architecture, refactoring, and disciplined release practices.
Benefits
• Discover the perks of being part of our vibrant team! We offer: • Remote Work Environment: Embrace the freedom to work from anywhere, anytime, promoting a healthy work-life balance. • Unlimited PTO: Enjoy unlimited paid time off to recharge and prioritize your well-being, without counting days. • Paid National Holidays: Celebrate and relax on national holidays with paid time off to unwind and recharge. • Company-provided MacBook: Experience seamless productivity with top-notch Apple MacBooks provided to all employees who need them. • Flexible Independent Contractor Agreement: Unlock the benefits of flexibility, autonomy, and entrepreneurial opportunities. Benefit from tax advantages, networking opportunities, reduced employment obligations, and the freedom to work from anywhere. Read more about it here: https://docs.google.com/document/d/1tzxGX4Uu7Ts_HCLFXESKLnKaaBfVCPf1f9AYZPrkjJM/preview?tab=t.0 https://docs.google.com/document/d/1nkrN76JlZkbKj9WSOhlT1_mni_CZeDkHdwfIjPXVwvk/preview?tab=t.0#heading=h.ndsdl4wapxtt • Be part of our fast-growing team and seize this excellent opportunity for personal and professional growth!
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