Yahoo! describes two systems for processing feeds at scale: Pacman and Pepper. Pacman uses Hadoop to process large feeds with millions of records, providing reliability and high availability. Pepper was developed for smaller feeds and uses a servlet model for synchronous in-memory execution to reduce overhead, providing isolation and scalability. Both systems leverage Hadoop and share the same infrastructure, with Pepper designed to serve as a cloud on top of Hadoop. Yahoo! routes feeds between the two systems based on size and other criteria to cover processing of all feeds.