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Tripadvisor is seeking a Principal Machine Learning Scientist to serve as the technical anchor for its core discovery engine in London. In this high-impact role, you will lead the machine learning strategy and execution powering how millions of users search for, discover, and organize complex travel itineraries. You will bridge cutting-edge AI research with production-grade engineering, directly influencing business outcomes like user engagement and booking conversion.
Key responsibilities include:
**Technical Leadership & Execution:** Drive the technical roadmap for Search, Retrieval, Ranking, and Recommendation systems within the Trips vertical. Translate business goals into concrete ML architectures and scalable production systems.
**Advanced Algorithm Innovation:** Design, prototype, and scale next-generation recommendation and ranking models. Solve complex, non-linear travel journeys using sequential recommenders, representation learning, and deep multi-objective frameworks.
**System Architecture & Scalability:** Oversee deployment of low-latency, high-throughput retrieval and ranking pipelines capable of processing billions of travel data points (reviews, photos, bookings, user intent) in real-time. Implement multi-stage retrieval and vector search systems.
**Cross-Functional Collaboration:** Partner with Product Managers, Engineering Leads, and Data Science peers to optimize multi-task business objectives. Act as the primary technical authority for ML initiatives within the Trips vertical.
**Talent Multiplier:** Mentor and coach senior and mid-level ML scientists. Foster a culture of technical excellence, driving best practices for MLOps, rigorous A/B testing, data privacy, and code quality.
**Required Qualifications:**
- Ph.D. or Master's degree in Computer Science, Machine Learning, Statistics, or highly quantitative field
- 8+ years of industry experience developing and deploying large-scale ML models in production
- Proven track record shipping systems at scale of millions of active users
- Deep expertise in Multi-Task Learning (MTL), Multi-gate Mixture-of-Experts (MMoE), or similar multi-objective optimization architectures
- Hands-on experience building sequential recommendation systems capturing real-time user session dynamics and long-term preferences
- Strong understanding of embedding generation, deep semantic retrieval, and multi-modal representation learning
- Mastery of Python and deep learning frameworks (TensorFlow, PyTorch)
- Experience with distributed computing (Spark, Ray) and cloud infrastructure (AWS/GCP)
**Desired Qualifications:**
- Strong experience with Graph Neural Networks (GNNs), knowledge graphs, or graph embeddings for mapping complex travel entity relations
- Familiarity with Agentic AI frameworks, LLM-driven reasoning, or autonomous planning agents
- Background in e-commerce, travel tech, or two-sided marketplaces handling non-linear user journeys and constrained inventory
- Publications in top-tier AI/IR conferences (SIGIR, KDD, RecSys, NeurIPS) or open-source ML contributions
