We're looking for a Staff Software Engineer to help build AI-native features into Factorial's product. You'll be writing Rails and React, designing systems, and shipping product hand in hand with Product and Design. "Our Engineering team is the engine behind Factorial, crafting the tech that makes HR simple, fast, and reliable for thousands of companies. If you love solving hard problems and want to build something that truly matters, come build it with us.We're a team of 200+ Product Engineers building Business Management solution that actually works for the people using it. 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.
You have solid depth in both backend and frontend software engineering
You understand APIs, cloud platforms (AWS, Azure, or GCP), and system design well
This is about building with AI, not training or fine-tuning models
You're seen as a technical and cultural leader,



and you hold the bar high
You push back on process that doesn't serve the team, from hiring to deployment
You communicate clearly in English; Spanish is a plus
As a Staff Engineer, you'll set technical direction for meaningful chunks of the roadmap, not just execute against it. This isn't occasional collaboration, it's a tight, ongoing partnership. Keeping it reliable once real customers depend on it is another. You'll build monitoring and quality tooling (automated and human-in-the-loop) so teams get a real signal on quality.
Ground AI features in data we actually trust. Whether it's mentoring, hiring, or pushing for better practices, you'll leave the engineering culture better than you found it.
One honest note: if you're mainly looking to do model training, fine-tuning, or applied ML research, this probably isn't the right role for you. We're a product engineering team working with LLM APIs and agentic s

📌 Staff Software Engineer (Barcelona)
🏢 Factorial Hr
📍 Barcelona