Staff Software Engineer

HelloWe'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 technical decisions and create things others across the company build onYou communicate clearly in English; Spanish is a plusWhat You’ll Be Doing?Lead technical initiatives. As a Staff Engineer, you'll set technical direction for meaningful chunks of the roadmap, not just execute against it. You'll make the calls on architecture and approach, and be accountable for how they play out.
Work very closely with Product. This isn't occasional collaboration, it's a tight, ongoing partnership. You'll shape what gets built alongside Product and Design from the earliest conversations, not just take specs and implement them.
Own systems end to end. From the first conversation about a problem, through production rollout, to long-term maintenance. Including the unglamorous parts.
Stay close to customers. The best technical decisions come from understanding real problems, so you'll talk to customers directly and bring that context back into how we build.
Help define how we build AI features at scale. We're still figuring out what great AI product engineering looks like at Factorial, and that's part of the job. You'll help shape how we design, build, and run AI-native product experiences so they're reliable, compliant, and genuinely useful.
Champion spec-driven development. Push for a culture where teams define what \"good\" looks like before they build: expected behaviors, constraints, edge cases, success criteria. Then use those specs to move fast without breaking things.
Build things other teams can reuse. Rather than a patchwork of one-off AI experiments, you'll build shared components other product domains can actually use: scalable, secure, and easy to govern.
Design and evolve AI Skills. Drive the creation of modular, reusable AI \"skills\" that automate real workflows and take safe, traceable actions inside Factorial's ecosystem, especially where finance is involved.
Build the tooling that keeps AI features trustworthy. Getting an AI feature to production is one thing. 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. Help define how we combine LLM outputs with deterministic sources of truth, balancing flexibility with accuracy and compliance.
Raise the bar across the company: Whether it's mentoring, hiring, or pushing for better practices, you'll leave the engineering culture better than you found itOne 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 systems, not a team building models from We Work ð» (Barcelona or Madrid Office)At Factorial, we believe the best products are built when people come together, in person to collaborate, challenge ideas, and move fast. That’s why our Engineering Teams follows an office-first, flexible s