A web page loads in under a second. In that second, a single user request may have passed through roughly ten distinct systems on its way to and from the database. The page feels fast because of how those systems are arranged. Each layer absorbs as much traffic as it can before passing the rest along. Taken together, the layers form a funnel, with most traffic handled long before it reaches the bottom.

Understanding what each layer does to narrow that funnel can lead to a better grasp of each component of a modern web stack.

In this article, we follow the journey of a web request one hop at a time. At each stop, we ask two questions. What is this layer doing, and what trade-off is it making? The journey starts before the request has fully left the browser, and latency is spent at every hop.