About the Role

We are seeking an experienced Staff Data Scientist with deep expertise in experimentation and ML frameworks (specifically search systems and recommendation engines) to join our dynamic team. Domain knowledge with large language models (LLMs) and post-training optimization is a key priority as we expand our AI capabilities.

Responsibilities

Our ideal candidate combines deep technical expertise in search and recommendations with practical experience in LLM systems, bringing a data-driven approach to improving user experiences through better content discovery and model performance.

• Design and implement search retrieval and ranking algorithms that surface the most relevant content to users

• Develop and optimize recommendation systems for personalized content discovery

• Support post-training optimization of LLMs through techniques like RLHF and DPO

• Create comprehensive offline evaluation frameworks to measure LLM performance, search quality, and recommendation relevance

• Design and execute online A/B testing initiatives to validate improvements across search, recommendations and LLM systems

• Drive continuous improvement in model behavior through quantitative analysis and user feedback

• Collaborate with engineering teams to implement and productionize algorithms

About You

You could be a great fit if you:

• Have 5+ years of experience at chat, social media, or consumer product companies, with substantial focus on ML frameworks

• Have deep expertise in testing, optimizing and measuring Large Language Models, search ranking algorithms, recommendation systems

• Able to design, drive and execute leaning into high velocity experimentation across consumer facing features

• Have a strong intuition for choosing the right questions to ask and quickly driving to key insights, particularly in evaluation of LLM, search and recommendation models and user engagement metrics

• Have extensive history of taking ownership and driving impact through data

Required Qualifications:

• Advanced degree in Computer Science, Statistics, Mathematics, Engineering or related field

• Strong programming skills in SQL, Python and experience with ML frameworks

• Strong background in retrieval, ranking algorithms, and relevance metrics

• Experience with modern search technologies (e.g., Elasticsearch, vector search) and recommendation frameworks

• Expertise in A/B testing and causal inference

• Excellent communication skills and ability to collaborate cross-functionally

Preferred Qualifications:

• Working knowledge of LLM architectures, fine-tuning and optimization techniques

• Work experience at an AI-centric product company

• Familiarity with prompt engineering and LLM offline and online evaluation frameworks

About Character.AI

Founded in 2021, Character is a leading AI company offering personalized experiences through customizable AI 'Characters.' As one of the most widely used AI platforms worldwide, Character enables users to interact with AI tailored to their unique needs and preferences.

In just two years, we achieved unicorn status and were named Google Play's AI App of the Year – a testament to our groundbreaking technology and vision.

Ready to shape the future of Consumer AI? 🚀

At Character, we value diversity and welcome applicants from all backgrounds. As an equal opportunity employer, we firmly uphold a non-discrimination policy based on race, religion, national origin, gender, sexual orientation, age, veteran status, or disability. Your unique perspectives are vital to our success.