Staff AI Engineer - API & Integrations Team (Madrid)
Confirmed on the employer's own hiring board on Oct 19, 2026. First seen by Alion on Jul 13, 2026. Factorial scores A on the Alion truth index.
Hello!
Do you want to help us build the platform that connects Factorial to the rest of the software world, with strong engineering foundations today and AI as a growing part of how we work tomorrow?
We're looking for engineers who:
Care about the maturity and quality of what they ship, more than the specific stack they use
Care about whether the thing they built actually worked - not what their title says
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 a Business Management solution that actually works for the people using it. Our core stack is Ruby on Rails and React, though we're open to engineers from other stacks - what matters most to us is the maturity of your development practice.
The API & Integrations team addresses particular challenges at Factorial. We sit at the intersection between product and platform. We own product surface while we also design developer experiences for internal and external developers of integrations.
We build tools for Factorial product teams to publish in our extensive public API.
We build an integrations framework to achieve the best user experience and developer experience when using integrations. Several Factorial products are already using this framework, and we keep expanding it.
We enable our developer partners to extend Factorial and live the best developer experience. With the acquisition of YepCode, we're laying the groundwork to bring AI further into how we build integrations.
Our mission is not only to unblock markets that rely on a fragmented market of different external software (payroll software solutions, ERPs, cloud-based identity services, etc.), but also to lower the barrier so that anybody (even HR managers) is able to create new integrations.
What You'll Do
As an engineer on the API & Integrations team, your main focus will be owning the development of our public API and integrations framework end-to-end, from problem definition and system design to shipping, monitoring, and iteration in production.
You will:
Own systems end-to-end
From problem definition and system design to shipping, monitoring and iteration in production.
Collaborate closely with Product and Design
Shape how the API and integrations framework serve real user needs, not just isolated technical components.
Work with a real cross-product consistency challenge: keeping the same user and integration experience across verticals (ATS, payroll, ERPs...), all tied to Factorial's design system and transparent to every product team.
Stay close to our customers
We have a strong customer-centric mindset: engineers regularly join customer calls, reviews, and feedback sessions to deeply understand real workflows, pain points, and constraints, ensuring we build the right solutions to real problems, not assumptions.
Share knowledge and raise the bar
Mentor peers, document learnings, and contribute to Factorial's engineering best practices.
Take ownership of AI as it takes shape
As we build on the YepCode acquisition, you won't be joining a finished AI roadmap, you'll be one of the people defining it: AI Skills, evaluation frameworks (Evals), RAG, and agentic workflows are all still taking shape, and we want someone who wants to build them, not just use them.
What are we looking for?
Your title matters less than your mindset.
You might be mid, senior, or staff. What we care about is:
Development maturity: you write solid, well-tested, production-grade code and can be trusted to own a system end-to-end
Proven impact: shipped projects, side projects, or contributions that made a measurable difference
Product-first thinking: you design complete experiences, not just isolated components
Speed & adaptability: you experiment, learn, and iterate fast
An abstraction mindset: real experience working with legacy/monolithic systems, with a track record of thinking in reusable, generic frameworks and components that serve multiple teams and languages, abstracting and generalizing solutions for multiple cases, rather than one-off, product-specific fixes.
Bonus points if you've worked with:
LLMs, skill-based agents, MCP, or other AI protocols are not required today, but relevant as our roadmap evolves.
Technical Foundation (Not Strict Requirements)
Strong candidates often have:
Solid software engineering fundamentals and development maturity, in any language (backend, frontend, or both)
Experience shipping real products to production
Knowledge of APIs, cloud platforms, and system design
A fast learning curve with new tools and technologies
We care far more about what you've built than the stack you used. Our team currently works with Ruby on Rails and React, but we're open-minded about candidates from other stacks. We're specifically looking for prior experience working with legacy/monolithic systems and evolving internal frameworks; the language itself doesn't matter, what matters is having gone through that kind of architectural challenge.
How We Work (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 follow an office-first, flexible schedule.
We work on-site several days a week, using that time to connect, align, and innovate as a team. However, we also understand the importance of focus and flexibility, so we support remote work when it makes sense - whether for deep work, personal needs, or just a change of scenery.
This balance helps us stay agile, creative, and closely connected, while giving everyone the space to do their best work.
At Factorial we don't evaluate you by years of experience but by your knowledge and skills.
We use our Career Path with a rubric framework where we define what is expected for each experience level and skill. This framework allows you to know your current level and what you need to keep growing. We love transparency, so our Career Path includes the salaries for each level, which we share during the first interview to ensure alignment.
Our Hiring Process
Intro Call → Chat with our Talent Partner about your journey and goals.
Hiring Manager Interview → Deep dive into your product mindset, teamwork, and problem-solving.
Live Challenge → A collaborative technical exercise based on real-life problems.
Final Coffee Chat → A relaxed conversation with our CTO & VP of Engineering to explore our vision, culture, and your growth.
The whole process is remote, using videoconferencing tools!
About Factorial
Factorial is the AI for Business that knows companies, connects how work happens across the business, and turns that context into action.
Founded in Barcelona in 2016, we now have +1,700 employees serving more than 16,000 companies across 112 countries.
Factorial started with a simple idea: companies were spending too much time managing processes and not enough time doing the work they were hired to do: their best work.
But as companies grow, work gets more disconnected. More people, more tools, more information, and more time spent connecting the dots. Generic AI can answer questions, but it doesn’t know your company. Every time, you have to give it the context.
Factorial is different. Because it’s inside the company, it already knows how it works, including its people, processes, policies, and data. So you can ask it to do real work, from screening candidates and managing expenses to answering questions and creating reports.
AI isn’t the goal. Giving people back their time is.
When work changes, so do we.
We believe in diverse talent: we welcome applicants from all backgrounds and strongly encourage people of diverse experiences and identities to apply.
We believe in inclusion: we are committed to equal opportunities and actively promote workplace inclusion of people with disabilities. If you would like to learn more about our inclusive recruitment processes, you are welcome to indicate so optionally and we will share additional information with you.
Our Values
We own it: We take responsibility for every project. We make decisions, not excuses.
We learn and teach: We're dedicated to learning something new every day and, above all, share it.
We partner: Every decision is a team decision. We trust each other.
We grow fast: We act fast. We think that the worst mistake is not learning from them.
Wanna learn more about us? Check our website!
Perks of being part of Factorial
High growth, multicultural and friendly environment
Competitive ESOP plan
Alan as private health insurance
Healthy life with Wellhub (Gyms, pools, outdoor classes)
Save expenses with Cobee
Language classes
Breakfast in the office and organic fruit
Food discounts with Nora
Pet Friendly
Much more that we'll spill during the interview process!