This position is at Factorial The selection process will be entirely managed by Factorial.
-- Hello
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 engineers who: Treat AI as central to their craft, not a feature to bolt on later Want to build and ship, not debate and document Care about whether the thing they built actually worked — not what their title says.
Ready to be part of the challenge?
As a Product Engineer you'll help us support and scale our AI-Driven Finance Domain to the next level.
Someone who gets involved from problem definition through to measuring whether the thing shipped actually helped, not someone who picks up a ticket, writes the code, and moves on.
We want people who are curious about why a feature exists, not just how to build it.
This is not a maintenance role.
We're moving fast, the domain is expanding, and there's real engineering work to do.
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.
Finance is one of the fastest-growing domains at Factorial.




Its mission is to be the financial backbone of the companies we serve, handling everything from expenses and invoices to payments, cards, accounting, and analytics so that teams can stop chasing paperwork and processes and focus on the decisions that actually move their business.
Where we're going is more ambitious.
We're building an AI platform that does the work for you: instead of processing invoices, you oversee a system that reconciles them, negotiates amendments with vendors, and closes out the payment cycle on its own.
We're extending our banking-as-a-service platform so companies don't just pay with cards and transfers but also get paid, through products like accounts receivable.
And we're turning Finance into an engine for cost reduction: planning headcount, policing spend, catching anomalies in invoices and contracts before money goes out, and surfacing the true cost of projects to protect margins.
It's a domain where the work has a direct, measurable impact on every company that uses us and where there's a lot still to build
What are we looking for?
?
You've shipped AI-powered features and know that evaluating them in production is the hard part, not building them.
You think about reliability and user friction before model complexity.
You're comfortable reviewing agentic workflows and have opinions about LLM architecture tradeoffs.
Not just theoretical ones.
You treat AI features as hypotheses.
Build, deploy, measure, adjust.
You own that whole loop, not just the build part.
You can break down non-deterministic outputs into something the rest of the team can reason about and act on.
You're comfortable working with Ruby on Rails

📌 Senior Product Engineer (Madrid)
🏢 Factorial
📍 Madrid