Staff Software Engineer

Factorial; Oleiros; On-site; EUR 90,000 - 120,000; Full time

Job summary

Factorial is seeking a Staff Software Engineer to help build AI-native features into our product. You’ll write Rails and React, design systems, and ship real features to production, working closely with Product and Design.

You’ll lead technical initiatives and set direction for meaningful parts of the roadmap, collaborating closely with Product. This role centers on building with AI APIs, not training models.

Qualifications

• Solid depth in both backend and frontend software engineering.
• Shipped real products to production, not just prototypes.
• Experience integrating LLM APIs into product features.
• Ability to lead technical decisions and influence roadmaps.

Responsibilities

• Lead technical initiatives and set direction for meaningful roadmap chunks.
• Collaborate closely with Product and Design from early conversations.

Skills

Backend & frontend

APIs & cloud platforms

LLM integration

Architectural design

Leadership

Tools

Rails

React

AWS

GCP

Azure

Job description

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.

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 side
• You lead key technical decisions and create things others across the company build on
• You communicate clearly in English; Spanish is a plus

What 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