Principal Software Engineer I - Data & AI - Marketplace

About Us: At Booking.com, data drives our decisions. Technology is at our core and innovation is everywhere. But our company is more than datasets, lines of code or A/B tests. We're the thrill of the first night in a new place. The excitement of the following morning. The friends you make. The journeys you take. The sights you see. And the food you sample. Through our products, partners and people, we can empower everyone to experience the world.

Role description: Marketplace Data & AI - mission and purpose

Marketplace Data & AI exists to turn Booking.com's scale into a competitive advantage. We build the intelligence products and data platforms that power how travelers discover, plan, and book - from the ranking and recommendation engines that shape every search result, to the traveller context models that make personalization possible across the entire Marketplace. We drive decisions through experimentation, building a culture of testing and measurement that extends beyond Marketplace to the wider company. We sit at the intersection of data engineering, machine learning, product thinking, and data science, and we're accountable for outcomes, not just capabilities.

Focus on intelligence products and the AI Application Platform

Within Marketplace Data & AI, this role spans four connected product areas.

AI Experiences combines the AI Application Platform (AIAP) with the AI applications (GenAI and more) built on top of it. AIAP is a product built on top of Booking.com's core Platform layer, purpose-designed to solve the engineering capabilities that Customer AI specifically requires. It is not a generic shared platform. It has a defined consumer and a clear product mandate. Sitting above it are the traveler-facing AI applications that AIAP enables, where we drive business impact and customer outcomes.

Benefits & Relevance is the intelligence and ML layer that powers how Booking.com ranks, recommends, and optimizes benefits. This covers ranking models, recommendation engines, and benefits optimization; the proprietary signal work that drives measurable commercial and traveler outcomes.

Experimentation is both a platform and a culture. We build the platform and engineering foundations that enable rigorous, data-driven decision making across Marketplace and the wider company, and this role helps set the standard for how experimentation is designed, run, and learned from.

Traveler Intelligence is our investment on building a unified understanding of the traveler - their context, preferences, intent, and behavior across the Booking.com ecosystem. It is the intelligence layer that makes personalization meaningful, and that feeds the AI products and experiences built across all other areas.

Across all four areas, we hold two things simultaneously: the discipline of a product organization - owners, roadmaps, accountability for outcomes, and the ambition to scale what we build beyond Marketplace to the whole company.

Role overview:

Principal Engineers are the technical leaders involved in key business initiatives. They own the technical strategy and co-create and drive the tactical plan to achieve these goals. They are role models, mentors, and strategists who oversee and execute technical tasks with excellence.

As a Principal Software Engineer, you will be responsible for setting the technical vision for the AI Application Platform and the intelligence products it enables, and defining the fundamental guidelines for architectural and technical design and the SDLC. These guidelines should employ specific reusable patterns and recommendations that can be applied to major product increments across Booking.com's intelligence capabilities.

This role requires deep domain knowledge in data and AI engineering - you understand how intelligence products are built end-to-end, from data pipelines and feature stores through to model serving, experimentation, and outcome measurement.

• Lead scoping and (re)design of various systems within the area, having a direct impact on the business, and on the experience of Booking.com's customers and partners.
• Define the engineering patterns and standards for building, evaluating, and operationalizing AI/ML capabilities across Marketplace - covering the full lifecycle from data to the deployed model to measurable business outcomes.
• Drive the technical direction of the AI Application Platform, ensuring it serves as a genuine accelerant for intelligence product development rather than another layer of complexity.
• Transform conceptual ideas into a specific set of artifacts (visualizations, list of capabilities etc.) by defining the scope, constraints, non-functional requirements, engaging and managing required stakeholders, identifying scenarios, and guiding principles.
• Serve as a tech lead on projects involving multiple teams across and beyond the business unit.
• Develop the technical strategy and engineering/architectural guiding principles for a set of engineering teams united under the same product/technical purpose.
• If required, hands-on development of proof of concepts and evaluation of new technologies.
• Guide the implementation of technical strategic decisions in cross-functional teams.
• Work closely with product owners, architects, and engineers to design, implement, and continually improve highly scalable, resilient applications and services.
• Provide technical guidance to other team members.
• Enforce sound technical standards.
• Advise product and engineering leadership on how to achieve strategic business objectives.
• Help align architectural solutions between business units.
• Strengthen the engineering community and coach senior engineers in their further development.

• 10+ years of software development experience and the last 3 years operating in a Technical leadership role
• Proven track record of driving successful complex technical initiatives within a large-scale organization
• Deep hands-on experience building and operating production ML or AI systems - you've taken intelligence capabilities from prototype to accountable product at scale.
• Practical knowledge of modern AI/ML infrastructure: feature platforms, model serving, experimentation frameworks, and the data pipelines that feed them.
• Experience working with GenAI and foundation models in a production context - you understand the trade-offs between LLM-based approaches and proprietary ML, and can make the call on which is right.
• Experience and understanding of how to design, develop, and operate strategic systems.
• Proven hands-on experience in designing, building, improving, and operating high-throughput, highly available, and scalable distributed systems in fast-growing environments.
• Proven experience in using enterprise integration patterns and defining non-functional requirements.
• Extensive experience with software development processes.
• Ability to design and solve complex business problems by defining the scope, principles, and constraints, engaging and managing stakeholders, identifying scenarios, and building prototypes if applicable.
• Fluency across the data and AI stack - from data engineering and ML frameworks to platform APIs and cloud infrastructure. Hands-on capability matters; this role leads by example.
• Ability to convince, provide clear work direction, and guidance to colleagues of various seniority.
• Excellent communication skills. Demonstrated ability to use data to influence and drive decisions.
• Strong customer focus and passion for doing the right thing for the customer.

• Annual paid time off and generous paid leave scheme including: parental (22-weeks paid leave), grandparent, bereavement, and care leave
• Hybrid working including flexible working arrangements, working from home furniture and ergonomic support, and up to 20 days per year working from abroad (home country)
• A beautiful sustainable HQ Campus in Amsterdam, that offers on-site meals, coffee, and snacks, multi-faith and breastfeeding rooms at the office
• Commuting allowance and bike reimbursement scheme
• Discounts & Wallet credits to spend on our products, upgrade to Booking.com Genius Level 3, and friends & family Booking.com discount vouchers
• Free access to online learning platforms, development and mentorship programs
• Global Employee Assistance Program, free Headspace membership

• The interview process will entail a total of 4 interviews, all conducted via Zoom video conferencing.