Ben Maurer kept things rolling with an end-to-end overview of the challenges of web performance at scale and the solutions Facebook has designed. Web pages can have multiple stages of completion — is it done when the first pixel renders? when the last element downloads? — so the first task is to define a metric that helps reflect the user experience. At Facebook, Ben and his team have found that Time-to-Interact (minimum usable page content) and Display Done (all page content) have been good metrics for guiding their work. Ben then showed off the tools they use to measure and analyze the data they collect. Finally, Ben showed us the tools Facebook has developed to make things faster. Downloading code is on the critical path of any web request and requires several creative solutions to mitigate. The team minimizes time to first byte on the client with Early Flush, prioritizes content within a response using Big Pipe, and provides frameworks for lazy-loading JavaScript with Bootloader.