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? ðAbout the team ðOur 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? ðYou have solid depth in both backend and frontend software engineeringYou've shipped real products to production, not just prototypes or proofs of conceptYou understand APIs, cloud platforms (AWS, Azure, or GCP), and system design wellYou've integrated LLM APIs into product features and shipped them to real users. This is about building with AI, not training or fine-tuning modelsYou're seen as a technical and cultural leader, and you hold the bar highYou push back on process that doesn't serve the team, from hiring to deploymentYou drive adoption of new abstractions and make sure others can actually use themYou've shipped things that made a measurable difference, at work or on the sideYou lead key

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