Job Overview
Location
European Union
Job Type
Full-time
Category
Software Engineering
Date Posted
July 9, 2026
Full Job Description
đź“‹ Description
- • We are looking for a Senior AI Engineer to own and drive the quality, reliability, and evolution of our AI systems in production.
- • This is a high-ownership role, responsible for end-to-end delivery of major AI features, production stability of AI systems, and data-driven experimentation using tools like Langfuse, Mixpanel, and OpenRouter.
- • You will work in a modern stack built on Next.js, TypeScript, Node.js, and Redis, collaborating closely with product, growth, data, and billing teams.
- • Increasingly, this includes building agentic, tool-using AI systems — defining clean tool contracts (including MCP-based tools) and orchestrating how AI interacts with internal services and business systems.
- • Our engineering organization uses a squad-based structure. You will operate within an AI engineering squad, contributing as a senior technical voice and driving engineering quality within your area of the product.
- • Key responsibilities include taking complete ownership and delivering major AI engineering features within agreed timelines, owning AI output quality, structure, and predictability across all user-facing AI interactions, designing, implementing, and maintaining output-type-based AI systems, and ensuring consistent output structure and formatting across different LLMs for the same request type.
- • You will also 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, and build and maintain complex, multi-step LLM workflows.
- • Additionally, you will 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.
- • You will also monitor AI system metrics, quality signals, latency, and release health using Langfuse and other observability tools, deep-debug complex LLM chains using Langfuse traces, and identify bottlenecks and optimise for cost, latency, and context-window usage.
- • Furthermore, you will write clean, scalable, and maintainable TypeScript code across the Next.js and Node.js stack, build reliable backend logic for AI systems, and ensure high code quality through testing, code reviews, and clear engineering standards.
🎯 Requirements
- • 6+ years of backend/full-stack software engineering experience, including production-grade TypeScript/Node.js.
- • 2+ years of experience building AI/LLM systems in production.
- • 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.
🏖️ Benefits
- • 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.
- • 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.
Skills & Technologies
See exactly how your profile matches this role — strengths, skill gaps, and what to do about them.
About Ruby Labs Ltd.
Ruby Labs Ltd. is a London-based product studio that builds and scales consumer subscription mobile and web applications. The company focuses on health, wellness, and productivity verticals, developing apps such as Hint, Able, and the award-winning fitness platform FitCoach. Using data-driven growth and proprietary technology, Ruby Labs rapidly prototypes, launches, and iterates products to serve millions of global users. The team combines engineering, product design, and performance marketing expertise to create sustainable digital businesses. Founded in 2018, Ruby Labs operates a portfolio of self-funded apps, emphasizing user privacy, scientific validation, and long-term customer value.
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