Over one billion hours of video are watched on YouTube daily, and the desktop YouTube site is built using Polymer. That brings with it some unique constraints and scalability challenges. The YouTube site is comprised of over 400 web components, developed by dozens of teams. In this video, YouTube Software Engineers Ziling Zhao and Mikhail Sychev explain how they were built. Check out the rest of the Polymer Summit session videos here: https://goo.gl/KuiAXd Subscribe to the Google Chrome Developers channel: http://goo.gl/LLLNvf