Staff ML Engineer

Factorial is building a world-class data and AI platform to help teams make smarter decisions automate complex workflows and deliver more value to our customers.

As a Staff ML Engineer youll set the technical direction for how we design build and ship AI-powered systems across Factorial. Youll own our most ambitious AI initiatives end-to-endLLM applications agents and assistantsand make them accurate reliable explainable and production-ready at scale.

Youll be a force multiplier: raising the engineering bar mentoring other engineers and partnering with Product Engineering Data Operations Sales and Customer Experience to turn the biggest business opportunities into robust AI solutionsbalancing speed impact correctness and long-term maintainability.

Youll be part of the Data Ops ML & AI team working within a fast-growing Engineering and Data organization that builds high-impact systems across Factorial.

You will identify design build and deploy AI solutions across the full lifecycle: from problem framing and prototyping to development productionization evaluation monitoring and continuous improvementand youll define the patterns and standards the rest of the team builds on.

A key part of the role is supporting our Data Scientists and Analytics team across the ML lifecyclehelping them take models and experiments from notebook to production providing the tooling pipelines and best practices they need and acting as the technical partner who turns their work into reliable maintainable systems.

Youll spend most of your time building with LLMs and modern AI frameworksdesigning RAG pipelines tool-using agents and assistants with LangChain and the surrounding ecosystem. Youll be expected to understand when an LLM-based approach is the right tooland when a simpler more deterministic solution is better.

Youll partner with stakeholders across the company to understand their needs define success metrics communicate trade-offs clearly and ensure the solutions we build are useful adopted and measurable.

Youll take ownership of projects from inception to production working autonomously while leading cross-functional efforts alongside Data Engineers Software Engineers Product Managers and business teamsand youll help others do the same through technical mentorship and design reviews.

We predominantly use Python SQL and modern AI tooling to build evaluate and deploy AI solutions. Youll write production-grade Python and work extensively with LangChain and the LLM ecosystembuilding RAG systems agents orchestration prompting strategies and evaluation harnesses.

Youll turn business questions into AI capabilities: defining the right interfaces retrieval strategies prompts tools and guardrails and validating them against clear measurable outcomes.

Youll develop LLM-powered applications and AI products ensuring they are well-tested observable cost-aware safe and aligned with business needs.

Youll collaborate with Engineering and Data teams to bring AI systems into production defining clear interfaces reliable pipelines monitoring and feedback loopsand establishing the architecture and best practices others reuse.

On the ML lifecycle side youll act as the engineering backbone for our Data Scientists and Analytics teampairing with them to productionize their models building the shared pipelines frameworks and monitoring they rely on and reviewing their work to ensure its reliable observable and maintainable in production.

Youll implement evaluation and monitoring practices to detect quality regressions hallucinations latency or cost issues and changes in user or business behavior.

Youll write documentation share findings join and lead technical conversations and communicate insights clearly to both technical and non-technical stakeholders.

Youll iterate in short development cycles testing assumptions quickly learning from results and improving solutions based on real-world impact.

Read a lot: Get to know Factorials product customers data ecosystem and current ML & AI initiatives.

Learn a lot: Pair with team members from Data Product Engineering and business teams to understand the main opportunities and challenges where AI can create value.

Analyze a lot: Explore use cases validate assumptions prototype quickly and help define clear success metrics and technical direction for our most impactful AI projects.

Build a lot: Lead and contribute to high-impact AI workflowsLLM applications agents retrieval evaluation and stakeholder-facing solutions.

Fail a lot: We encourage experimentation. We understand that trying out new ideas failing learning and improving is part of the role.

Talk a lot: Participate in and lead team rituals and stakeholder sessions to ensure what we build solves real business needs and can be adopted effectively.

A degree in Computer Science or a closely related technical field.

5 years of experience as a Machine Learning Engineer Software Engineer or similar role with a strong track record of taking AI or data-intensive systems to production.

Strong software engineering fundamentals and excellent Python development skillsyou write clean tested maintainable production code.

Hands-on experience building LLM-powered applications with LangChain (or equivalent frameworks)RAG agents tool use prompting and evaluation.

Deep experience across the full lifecycle of AI/ML systems: from problem definition and prototyping to deployment evaluation monitoring and iteration.

Strong analytical skills and the ability to translate ambiguous business questions into structured measurable problems.

Solid experience with SQL and familiarity with the modern AI/LLM ecosystem.

Experience with production-oriented workflows including evaluation testing monitoring documentation and collaboration with Engineering teams.

A demonstrated ability to influence technical direction set standards and mentor other engineers.

Excellent stakeholder management skills with the ability to communicate clearly with both technical and non-technical audiences.

A strong ownership mindset autonomy curiosity and the ability to navigate ambiguity.

Comfortable working in English and with distributed teams.

Willingness to work from our Barcelona office 4 days per week with 1 day working from home.

Strong plus:

Experience deploying and scaling LLM systems in production (latency cost reliability safety).

Experience with LLMOps and MLOps practices and tools (orchestration evaluation observability vector databases).

Experience with retrieval systems embeddings and prompt/agent evaluation.

Experience working in SaaS B2B products HRTech fintech or business management software.

Experience leading cross-functional initiatives with Product and Engineering teams.

We follow an office-first flexible approach because we believe the best products are built when people collaborate face-to-face.

For this role were looking for someone who can work from our Barcelona office 4 days per week with 1 day working from home. This helps the team connect brainstorm align with stakeholders and ship together while keeping flexibility for deep work and personal balance.

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

High growth multicultural and friendly environment

Continuous training and learning based on your needs

Alan private health insurance

Healthy life with Wellhub (Gyms pools outdoor classes)

Save expenses with Cobee

Language classes with Preply

Get the most out of your salary with Payflow

And when at the office...

Breakfast in the office and organic fruit

Nora and other discounts

Pet Friendly

Diversity is part of our culture we have more than 43 nationalities in our teams and we are infused in an inclusive environment for all employees and candidates. Please feel free to apply with the way it suits you better! (blind resume identity pronouns cover letter etc). We do not discriminate on any aspect in fact; Factorial encourages everyone to join us!

Factorial is an innovative Business Management Software solution designed to streamline company processes for small and medium-sized enterprises. Founded in 2016 our mission is to help companies automate workflows centralize people data and make better business decisions. With customers across over 60 countries worldwide weve built a diverse team thats driving change in the business management tech space. Join us as we continue our rapid growth journey!

We own it: We take responsibility for every project. We make decisions not excuses.

We learn and teach: Were dedicated to learning something new every day and above all sharing it.

We partner: Every decision is a team decision. We trust each other.

We grow fast: We act fast. We believe that the worst mistake is not learning from them.