CodeRabbit is an AI-first PR Review tool that utilizes GPT APIs for various functionalities, offering a paid service called CodeRabbit Pro for private repositories, a free service called CodeRabbit for Open Source for public repositories, and a free plan for private repositories. The company aims to provide affordable, AI-driven code review services to developers and organizations of all sizes while supporting the open-source community. To achieve this, CodeRabbit uses large language models such as gpt-4, but also employs cost optimization strategies like dual-models, rate-limiting, and caching to manage costs effectively. By implementing these strategies, CodeRabbit reduces its costs by 50% on summarization and 20% on re-generating similar review comments, while providing a robust and free plan for open-source projects.