# Senior Machine Learning Engineer - Foundation Models
## About the role
We are seeking a Senior Machine Learning Engineer for our Foundation Models team, which focuses on building next-generation Generative AI and foundation model capabilities that enable intelligent experiences on eBay at global scale.
## Responsibilities
- Design, build and productionize machine learning and Generative AI capabilities for large-scale e-commerce applications
- Build and optimize systems with LLMs, retrieval-augmented generation, embeddings, multimodal models, ranking and personalization
- Develop learning systems that improve based on feedback signals, including reinforcement learning, preference optimization, reward modeling, bandits and online/offline feedback loops
- Collaborate with applied researchers to transform prototypes and experiments into maintainable production capabilities
- Build robust training, fine-tuning, evaluation and deployment pipelines for large-scale machine learning models
- Improve model quality, latency, cost, reliability and observability in production AI systems
- Integrate AI capabilities into eBay experiences in collaboration with engineering, product and platform teams
- Apply strong software engineering practices including code quality, testing, monitoring, documentation and operational excellence
- Stay informed of recent developments in machine learning, Generative AI and foundation models and help bring relevant innovations to production
- Elevate scientific and technical standards through structured experimentation, peer review and thoughtful technical contributions
## Requirements
- Master's, PhD or equivalent experience in Computer Science, Machine Learning, Artificial Intelligence, Computational Linguistics or related field with 8 years of relevant work experience
- Strong hands-on experience building and deploying machine learning systems in production environments
- Deep knowledge of machine learning, NLP, Large Language Models, neural architectures, embeddings, retrieval, ranking or multimodal modeling
- Experience with model training, fine-tuning, evaluation, deployment and performance optimization
- Experience with reinforcement learning or feedback-driven learning systems, including preference learning, reward modeling, bandits or continuous model improvement loops
- Demonstrated proficiency in software development with Python and experience with modern ML frameworks
- Experience with scalable data processing, distributed systems, cloud infrastructure or model-serving platforms
- Ability to design practical solutions that balance quality, latency, cost, reliability and maintainability
- Strong problem-solving skills and ability to work independently in ambiguous technical areas
- Excellent collaboration and communication skills with experience working with research, engineering, product and platform teams
- Strong sense of ownership and track record of delivering high-impact technical work as an individual contributor