Personalization is a key component in ensuring user satisfaction, and at Yahoo, personalization is at the heart of several user-facing products. This talk, between Yahoo Research Director of Personalization Suju Rajan and journalist Signe Brewster, focuses on how Yahoo built one of the largest news recommendation engines in the world: the Yahoo stream, which personalizes the news feed for several hundreds of millions of users on millions of content items. Beyond the scale, the success of the news feed also depends on whether it is able to engage the user long term. Suju presents the challenges and issues in designing an engaging stream, and tells attendees at the Structure Data 2016 Conference how to cope with sparsity of explicit feedback, how user behavior changes with context of the device, how to build machine-learned models for each user, and the metric that allows Yahoo to optimize for long term user-engagement.