Vercel, a platform for building, deploying, and scaling web applications, used Edge Middleware to run A/B tests on its new Templates page without sacrificing performance. The testing solution involved running code before serving requests from the edge cache, enabling developers to perform rewrites at the edge to show different variants of the same page to different users. This allowed Vercel to collect data and iterate through multiple release phases, including Early Access, Public Beta, and General Availability, without layout shift issues. Edge Middleware also helped avoid skeleton loaders on dynamic landing pages by detecting query parameters in the request URL and rewriting to a special route that shows a skeleton loader. The testing process involved collecting data points, tracking conversion rates with Heap, and using Algolia's Search Without Results feature to understand template search and filter usage.