Hello

We're looking for a Staff Software Engineer to help build AI-native features into Factorial's product. Not a researcher, not a model trainer: a product engineer who builds with LLM APIs the same way we build with any other API, shipping real features to real customers in production.

At Factorial, being a Staff Engineer means leading technical initiatives and working very closely with Product, not operating at arm's length from the roadmap. You'll be writing Rails and React, designing systems, and shipping product hand in hand with Product and Design. "AI" is the domain you'll work in, not a different job.

Ready to be part of the challenge? ?

About The Team ?

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.

What are we looking for? ?

You have solid depth in both backend and frontend software engineering
You've shipped real products to production, not just prototypes or proofs of concept
You understand APIs, cloud platforms (AWS, Azure, or GCP), and system design well
You've integrated LLM APIs into product features and shipped them to real users. 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 drive adoption of new abstractions and make sure others can actually use them
You've shipped things that made a measurable difference, at work or on the

📌 Staff Software Engineer (Barcelona)
🏢 Factorial
📍 Barcelona