Staff AI Engineer

Do you want to help us redefine how AI powers the future of Business Management software, not as an add-on, but as a core part of how people work, decide and grow?

We're looking for a Staff Engineer to lead the integration of artificial intelligence as a foundational element within our Business Management Software platform, rather than treating it as an auxiliary feature. Our core stack is Ruby on Rails and React, but the interesting work right now is what we're building on top of that: agentic workflows, LLM-integrated features, systems that behave probabilistically rather than deterministically.

What You'll Do:

• AI Architecture Definition: Shape how Factorial designs, builds, evaluates, and operates AI-native product experiences at scale.
• Specification-Driven Development: Establish practices where teams define success criteria and expected behaviors before implementation.
• Shared Foundations: Develop reusable AI capabilities and abstractions for cross-functional adoption.
• AI Skills Design: Create modular, reusable components for automating workflows with traceable actions.
• Evaluation Frameworks (Evals): Build assessment systems combining automated and human oversight for quality assurance.
• Data Grounding Strategies (RAG): Define retrieval approaches balancing probabilistic models with deterministic truth sources.
• Workflow Architecture: Design human-in-the-loop and agentic workflows combining LLMs, rules, and user oversight.
• End-to-End Ownership: Guide projects from conception through production and maintenance.
• Customer Engagement: Maintain direct connection with users to inform technical decisions.
• Cross-Functional Partnership: Collaborate with Product, Design, and Leadership teams.
• Cultural Leadership: Mentor colleagues and elevate engineering practices.

What we're looking for:

• Solid backend and frontend engineering depth.
• Cloud platform experience (AWS, Azure, or GCP).
• Shipped production products beyond prototypes.
• Strong APIs, cloud infrastructure, and system design understanding.
• Technical and cultural leadership presence.
• Experience building real AI-powered systems or workflows, not just tinkered with them.
• Measurable product impact achievements.
• Key technical decision-making history.
• Clear English communication; Spanish is advantageous.

Work arrangement: Office-first, flexible schedule, with emphasis on in-person collaboration several days weekly in Barcelona, supporting remote work for focused tasks.

Benefits: Private health insurance (Alan), fitness memberships (Wellhub), expense savings platform (Cobee), language training, office meals and organic fruit, food discounts (Nora), pet-friendly environment.

Factorial is Europe's fastest-growing SaaS company with 1,500+ employees globally, providing Business Management Software across HR, Finance, Talent, Operations, and IT domains.