Our client, a fast-growing international digital marketplace, is building AI-powered products that connect millions of users with trusted service professionals. Operating at large scale, the platform processes high volumes of data and interactions every day, with AI playing a central role in improving matching, trust, automation, and decision-making across the ecosystem. To support this vision, the company is expanding its senior technical leadership and is looking for an AI Principal Engineer to join its Barcelona-based engineering hub. In this strategic role, you will sit one level above Senior Engineers, owning a broad end-to-end technical view across systems, architecture, and AI-driven solutions. You will help define where and how AI creates the most value, while guiding teams to turn advanced ideas into reliable, production-grade systems. Your responsibilities and impact as an AI Principal Engineer: Architecting large-scale AI systems, including orchestration frameworks and AI-powered APIs. Defining how AI services are integrated across the platform through robust API designs. Guiding and mentoring senior engineers working on advanced AI and system design challenges. Partnering closely with engineering leadership to translate AI research into scalable systems. Setting technical standards and best practices for AI engineering, system design, and performance. Providing hands-on technical direction while influencing strategy across the wider engineering organisation. Skills, qualifications, and interests you need to succeed in this role: Deep experience designing and building distributed systems at scale. Strong background in API-based architectures and service integrations. Hands-on exposure to AI technologies such as LLMs, AI APIs, vector databases, or multi-agent systems. Ability to move from prototype to production, balancing experimentation with engineering discipline. Strong architectural instincts and a clear understanding of performance and scalability trade-offs. Confidence communicating technical direction and mentoring senior engineers. Experience in large-scale digital platforms or marketplaces is a plus. Fluent English required; Spanish is a plus. What’s in it for you? Competitive salary package aligned with a principal-level role. Paid annual leave and Sick leave. Maternity, paternity, and partner leave. Long-term opportunity in a company where AI is a core strategic pillar. High-impact role with strong autonomy and influence on technical direction. Barcelona-based position within an international engineering environment. Your future company You will join a well-established yet fast-evolving international tech company, trusted by millions of users and professionals. With AI deeply embedded in its platform strategy, the company continues to invest in cutting-edge technology to simplify complex processes, improve trust, and deliver meaningful impact at scale.