Machine Learning Scientist

As a Senior Machine Learning Scientist, you will design, build, and deploy uplift models and causal inference systems that allocate promotional spend across Booking.com’s accommodation marketplace. The role combines causal methodology, neural network architecture design, and production ML - with your work validated through large-scale A/B experiments. There are opportunities to publish applied research at top venues when the work contributes novel methodology., * Design and deploy uplift models that estimate heterogeneous treatment effects, optimising incremental return on investment under budget constraints.

• Design and execute causal inference methodologies; including observational debiasing (IPW, doubly robust estimation), sensitivity analysis, and interference-aware evaluation to close the gap between offline metrics and online impact.
• Advance the team’s neural network architectures for uplift modeling on tabular data (attention mechanisms, multi-head designs, self-supervised pretraining), balancing model expressiveness with production latency requirements.
• Research marketplace interference and cannibalization; building frameworks to measure and correct for demand shifting when partial treatment is applied across competing properties.
• Develop offline evaluation methods that reliably predict online performance, accounting for biases introduced by non-stationary treatment policies and interference effects.
• Own models end-to-end; from research through A/B experimentation to production calibration.
• Collaborate cross-functionally with ML engineers on pipeline and serving design, with data scientists on feature engineering, and with product and business stakeholders on spend strategy and ROI trade-offs.
• Actively coach and mentor less experienced team members, setting technical direction and providing guidance on causal modeling best practices.

• MSc or PhD (or equivalent experience) in a quantitative field such as Computer Science, Statistics, Economics, Econometrics, Operations Research, Mathematics, or Physics.
• Relevant professional or academic experience applying Machine Learning to business problems (typically MSc + 4 years, or PhD + 2 years).
• Advanced knowledge and experience in Causal Inference, Uplift Modeling, or Treatment Effect Estimation. Experience with heterogeneous treatment effects, interference / spillover effects, or policy learning is highly valued.
• Proven track record designing and executing end-to-end R&D plans, and generating measurable impact through large-scale ML model development. Evidence such as peer-reviewed publications, patents, or open-source contributions is a plus.
• Strong proficiency in Python and modern ML frameworks (e.g., TensorFlow, PyTorch, LightGBM, XGBoost).
• Solid understanding of experimental design, A/B testing, and statistical methodology - including awareness of SUTVA violations, selection bias, and observational study limitations.
• Experience working with large-scale data systems and production ML pipelines (Spark, Airflow, or similar).
• Experience with neural network design for structured/tabular data (embeddings, attention, multi-task architectures) is a strong plus.
• Experience collaborating cross-functionally with developers, analysts, product managers, and other scientists to deliver ML-powered products.
• Excellent English communication skills, both written and verbal. Ability to communicate complex causal reasoning clearly to both technical and non-technical audiences.
• Successfully driving technical initiatives and cross-team collaboration while communicating with stakeholders at all levels.

Booking.com’s Total Rewards Philosophy is not only about compensation but also about benefits. We offer a competitive compensation and benefits package, as well unique-to-Booking.com benefits which include:

• Annual paid time off and generous paid leave scheme including: parent, grandparent, bereavement, and care leave
• Hybrid working including flexible working arrangements, and up to 20 days per year working from abroad (home country)
• Industry leading product discounts - up to 1400 per year - for yourself, including automatic Genius Level 3 status and Booking.com wallet credit

Inclusion at Booking.com:

Take it from our Chief People Officer, Paulo Pisano: “At Booking.com, the diversity of our people doesn’t just create a unique workplace, it also creates a better and more inclusive travel experience for everyone. Inclusion is at the heart of everything we do. It’s a place where you can make your mark and have a real impact in travel and tech.”

Read all about Inclusion and the Employee Resource Groups (ERGs) at Booking.com here

Career Development Opportunities

• Learn more about Your Career Journey here.
• Become a Mentee and benefit from a mentoring relationship with a more experienced person to help you identify and achieve your professional and personal development goals.

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 next 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 make it easier for everyone to experience the world.