PageSpeed will make a best effort to expire its asset (.css, .js, .png, .gif, .jpg) cache periodically. During periods of rapid changes, automatic expunction may lag behind changes pushed to a server necessitating a manual flush of the cache.
Expunging PageSpeed cache
PURGE header may be sent to the asset forcing PageSpeed to expunge its cached copy from memory. For example to accomplish this using cURL from the terminal:
curl -v -X PURGE http://web.site/asset/style.css
To expunge every entry under a common URL or on a web site, use an asterisk:
curl -v -X PURGE http://web.site/asset/*
- Flushing PageSpeed Server-Side Cache (developers.google.com)