Senior Data Scientist (Hybrid @ Bellevue, WA or Remote @ Florida)

Team Charter:
The Data team is the engine of intelligence at OfferUp. Our mission is to transform massive amounts of marketplace data into seamless, safe, and personalized experiences that empower millions of people to connect and prosper. We bridge the gap between complex algorithms and real-world customer impact across search, trust & safety, and personalization.

About the role:

OfferUp is looking for a Senior Data Scientist to join our Data team and serve as a key architect of our marketplace intelligence. In this role, you will move beyond building models to defining the logic of the customer journey and driving the technical strategy for our most complex business problems. From optimizing search ranking and recommendation engines to pioneering fraud detection and generative AI features, your work will have a company-wide impact and be critical to OfferUp’s success as the leading local marketplace.

We are looking for a Senior Data Scientist to join our Data team. This team is tasked with building the core intelligence—from search ranking and recommendation engines to fraud detection and generative AI features—that is critical to OfferUp’s success as the leading local marketplace.

What we love about this role:

• Breadth of Impact: You won't be siloed; you will have the opportunity to drive results across Search & Discovery, Trust & Safety, Advertising, and core Personalization.
• Modern AI Stack: Access to a world-class infrastructure including DataBricks for training/registry, SageMaker for inference, and the ability to integrate LLMs into production workflows.
• Customer-Centric Research: The freedom to conduct deep research and experimentation while keeping the "human in the loop," ensuring our models delight users rather than just optimizing metrics.
• Collaborative Environment: Work alongside a high-powered engineering team that handles the heavy lifting of infrastructure, allowing you to focus on high-level modeling and experimental design.

In this role, you will

• 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.

Here’s more of what you will get to do:

• Impact on Product: 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.
• Impact on Company: Directly influence key business KPIs (e.g., conversion, retention, fraud reduction) by identifying untapped opportunities within our BigQuery data warehouse.
• Critical Projects: 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.

You’ll thrive in this role if you have:

• 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.

Helpful, but not required:

• Experience deploying models as microservices within cloud infrastructure (AWS preferred).
• Hands-on experience with Spark for large-scale data processing.
• Working knowledge of deep learning methods applied to images (CNNs, ResNet).

Compensation Range: $190,000 - $220,000

OfferUp offers a comprehensive compensation and benefits package where you’ll be rewarded based on your performance and recognized for the value you bring to the business. Individual salaries within our ranges are determined through a variety of factors, including but not limited to education, experience, knowledge, skills, and geography. All roles will receive equity in OfferUp as part of their compensation, the amount of equity varying depending on the individual’s level and experience.

Benefits (all US roles): In addition to our compensation package, this role is eligible to enroll in health insurance, healthcare savings and spending accounts, retirement savings benefits (401(k) plan with match), basic and voluntary life insurance, disability benefits, and paid time off for sick leave, family and/or medical leave, vacation, and 12 company holidays. In regard to vacation time, OfferUp has a flexible vacation policy, and, in general, full-time, exempt employees will be expected to take 3-5 weeks (15-30 days) of pre-planned vacation time per year. Vacation needs are flexible and will naturally vary from year to year based on individual circumstances and business needs. In regard to sick time, all full-time employees (exempt and non-exempt) will be granted 12 days (96 hours) of sick time per year (pro-rated if the start date is other than January 1). Your recruiter can share more details about specific benefits during the interview process.