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• Senior Product Engineer - Authentication Team

• Permanent
• Full time
• €60,500 - €77,000
• Barcelona, CT, Spain
• Engineering

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 and what is the exact value they’re adding.

Ready to be part of the challenge? 🚀

We are looking for a Product Engineer to join our CIAM (Customer Identity and Access Management) team at Factorial. You will work across the stack with a stronger focus on backend development.

You will be part of the team responsible for Authentication and Authorization at Factorial, driving a pragmatic balance between security and usability across a wide range of use cases. You’ll design and implement reliable, scalable identity solutions, collaborate with product and security stakeholders, and help shape our roadmap to deliver a seamless and secure experience for millions of users.

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.

You’ll be on the Customer Identity and Access Management (CIAM) team owning areas such as Authentication, Single Sign‑On, Multi‑Factor, Authorization, Permissions and Auditing. Sitting within the Platform Domain, you will lay the foundations that allow both external and internal users to extract and deliver value from our platform. You’ll also lead the team that tackles Factorial’s first scalability challenges, designing repeatable solutions and patterns that serve as a reference for the rest of the company when they encounter similar issues.

The role requires full ownership of your area, a self-starter attitude, dealing with uncertainty and combining a strategic product mindset with a focus on execution. If you feel as if you belong in a product-first company, want to work with a world-class team of designers and developers, and deliver the future of B2B software, we should talk!

What are we looking for? 🎯

• Strong backend experience building scalable, reliable systems (distributed systems, APIs, databases).

• Practical knowledge of authentication and authorization concepts (OAuth2, OIDC, JWT, SSO, MFA).

• Hands‑on experience with Ruby on Rails and frontend collaboration using React and TypeScript.

• Familiarity with observability, testing, CI/CD and incident response practices.

• Product-minded engineers who balance security, usability and time‑to‑market.

• Excellent collaboration and communication skills in English; experience working in cross‑functional teams (product, security, frontend).

• 5+ years of professional engineering experience (or equivalent demonstrable experience).

What you’ll be doing?

• Own and evolve critical CIAM capabilities: Authentication, Single Sign‑On, Multi‑Factor, Authorization, Permissions and Auditing.

• Design and implement scalable backend services and APIs used by internal and external products.

• Lead the team in identifying and solving Factorial’s earliest scalability challenges, creating repeatable patterns and best practices for the company.

• Collaborate closely with product, security and frontend teams to deliver secure, user‑friendly identity flows.

• Improve reliability and observability: monitoring, alerting, SLOs and incident management for CIAM services.

• Mentor teammates, conduct code reviews and help shape the technical roadmap and architecture for identity services.

How We Work 💻 (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 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

1. Intro Call → Chat with our Talent Partner about your journey and goals.

2. Hiring Manager Interview → Deep dive into your product mindset, teamwork, and problem-solving.

3. Live Challenge → A collaborative technical exercise based on real-life problems.

4. 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 🚀

At Factorial, we’re building the leading AI Business Management Software for companies of all sizes. Our platform centralizes key workflows across HR, Finance, Talent, Operations, and IT, freeing teams from manual processes so they can focus on what really matters: leading, growing, and taking care of their people.With over 1,500 employees across Europe, Asia, Africa, and America. We are one of Europe’s fastest-growing SaaS companies, proudly headquartered in Barcelona. If you're excited to shape the future of business management technology, we’d love to meet you.

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

• 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!