AI Engineer - API & Integrations Team

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
• ⚡ Are obsessed with building and shipping fast
• 🎯 Care about real impact, not hierarchy or titles

If that sounds like you, keep reading.

The Team 🧩

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 will be boosting how we build integrations, placing AI at the center of the process.

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 a Product AI Engineer at Factorial, you’ll help define and build the next generation of our AI-native product using modern AI development practices.

You will:

• Build product using Spec Driven Development

We define clear specifications before shipping — including expected behaviours, constraints, and success criteria — and use them to guide implementation, iteration and evaluation using most powerful LLMs.

• Design and implement AI Skills

Create reusable, well-scoped AI capabilities that can automate and take actions safely within Factorial’s workflows, and also when building integrations

• Develop and maintain evaluation frameworks (Evals)

Measure quality, correctness and reliability of AI outputs using automated and human-in-the-loop evaluations to ensure continuous improvement in production.

• Apply Retrieval-Augmented Generation (RAG)

Build systems that ground AI responses in trusted, up-to-date company data, balancing probabilistic models with deterministic sources of truth.

• Design human-in-the-loop and agentic workflows

Combine LLMs, rules, and user oversight to automate real business processes while keeping humans in control of critical decisions.

• Own systems end-to-end

From problem definition and system design to shipping, monitoring and iteration in production.

• 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.

• Collaborate closely with Product and Design

Shape how AI is embedded into core user experiences — not as a feature, but as part of the workflow.

• Share knowledge and raise the bar

Mentor peers, document learnings, and contribute to Factorial’s AI engineering best practices.

Who This Is For 🧠

Your title matters less than your mindset.

You might be mid, senior, or staff. What we care about is:

• AI as a habit: you’ve built real AI-powered systems or workflows (not just experiments)
• 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

Bonus points if you’ve worked with:

LLMs, skill-based agents, MCP, or other AI protocols 🤖✨

Technical Foundation (Not Strict Requirements) 🧱

Strong candidates often have:

• Solid software engineering fundamentals (any language — backend, frontend, ML)
• 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.

How We Work 🏢

• Office-first in Barcelona & Madrid, with 20% remote flexibility
• A people-first, high-trust culture built on radical candor and ownership
• A multicultural team (40+ nationalities) building the next generation of business management software

About Us 🚀

At Factorial, we’re building the leading business management software for companies of all sizes. Our platform centralizes key workflows across HR, finance, and operations, freeing teams from manual processes so they can focus on what really matters: leading, growing, and taking care of their people.With over 1,200 employees across 7 markets, we serve 700,000+ users and are one of Europe’s fastest-growing SaaS companies, backed by top-tier investors and proudly headquartered in Barcelona.We believe in bold goals, radical ownership, and inclusive collaboration. If you're excited to shape the future of business management technology, we’d love to meet 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.
• 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.

Wanna learn more about us? Check our website!

Perks of being part of our team💆

We care about people and we also offer a lot of benefits for employees:

• 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 🍏
• Nora discounts 🍱
• Free caffeine and theine ☕
• Pet Friendly 🐕