Hybrid Senior Data Scientist – Hybrid, Bellevue, WA, Florida

at OfferUp

• Job title: Senior Data Scientist – Hybrid, Bellevue, WA, Florida
• Job type: Full Time
• Experience level: Senior
• Salary: $190,000 - $220,000 per year
• Degree requirement: Bachelor's Degree
• Tech skills: BigQuery, Cloud, Distributed Systems, Keras, Python, PyTorch, SQL, Tensorflow
• Location requirements: Hybrid, Bellevue, United States

About the role

• Senior Data Scientist architecting marketplace intelligence at OfferUp. Driving ML solutions for optimizing search ranking, recommendation engines, and fraud detection features.

Responsibilities

• Lead the research, design, and implementation of end-to-end machine learning solutions, from initial hypothesis and data exploration to A/B testing and production deployment.
• Own the evaluation and "prompt engineering" strategy for Large Language Models (LLMs) to enhance product features like automated categorization and user communication.
• Act as a strategic partner to Product and Engineering leaders, translating business goals into data science roadmaps that prioritize long-term customer experience over short-term gains.
• Drive the next generation of Search and Personalization features; use LLMs to create "magic moments" for users while ensuring model outputs are safe, accurate, and valuable.
• Directly influence key business KPIs (e.g., conversion, retention, fraud reduction) by identifying untapped opportunities within our BigQuery data warehouse.
• Optimize our search ranking algorithms using modern learning-to-rank techniques; develop a robust framework for assessing and deploying LLM-based agents; refine our "Crime Risk" and user reputation models to maintain a safe marketplace.

Requirements

• 5+ years of building and shipping ML models and data solutions with quality.
• 4+ years of professional software development in Python.
• Strong proficiency in querying and retrieving data using SQL from large-scale distributed systems.
• Ph.D. or Master’s Degree in Computer Science, Mathematics, Statistics, or a related technical field OR Bachelor’s degree and relevant work experience.
• Deep understanding in a classical NLP method (e.g. n-grams, NER, POS tagging) and ML tasks (e.g. semantic analysis, text classification).
• Practical experience with LLMs, deep models (RNN, LSTM) and their applications is highly preferred.
• Proficiency in deep learning frameworks such as PyTorch, TensorFlow or Keras.
• Experience training models in cloud environments (Databricks/Sagemaker preferred).
• Proven track record of mentoring junior or mid-level team members and performing high-quality code and design reviews.
• Collaborative mindset with experience contributing to project roadmaps and technical documentation.
• Impact-oriented: Experience delivering end-to-end projects that solve complex business problems.
• Strong communication skills, with the ability to explain technical concepts to non-technical stakeholders.

Benefits

• Health insurance
• Healthcare savings and spending accounts
• Retirement savings benefits (401(k) plan with match)
• Basic and voluntary life insurance
• Disability benefits
• Paid time off for sick leave, family and/or medical leave, vacation, and 12 company holidays
• Flexible vacation policy