Yahoo! serves nearly 600 million unique users globally, reaching almost half the online global population. Achieving that level of ubiquity in people’s online lives introduces a whole new set of challenges. Scale requires optimal performance across geographic boundaries, creates mountains of data, attracts spammers and abusers, overloads commodity technology and generally just makes everything harder and more complex. To successfully operate and continuously innovate at this global scale requires robust and extensible tools. Cheryl will review two case studies where Yahoo! was able to solve problems of scale efficiently by using tools developed by Yahoo! engineers. The first case study will describe how Yahoo! used Hadoop to crunch massive amounts of data. With this technology, operations engineers where able to deliver a new spam-fighting system within weeks. The second will describe the use of YTS to provide optimal performance at huge scale across the globe, allowing Yahoo! to reach new markets.