Some people do use nginx as a caching server. CloudFlare, for example, is built on top of it.<p>The reason to do so is because you want the rest of what nginx provides, not to get its caching module. It is an extremely barebones solution that only solves the most basic requirements. I can only presume that CloudFlare and others have written their own caching modules for nginx.<p>A short list of annoyances:<p>1. No support for multiple disk devices. Files are written to a fixed temp path and then renamed to their real destination. So you need to use RAID to present the disks as one logical device, which is a wholly unnecessary expense in a caching environment.<p>2. No support for purging in open source. This is an nginx plus feature, which starts at $1900&#x2F;server&#x2F;year.<p>3. Because of the temp file &#x2F; rename thing, support for streaming subsequent requests off of the first request that is filling cache is janky. Subsequent requests have to acquire a lock.<p>4. No support for any fancier cache setups, utilizing ICP &#x2F; HTCP.