I don’t use Cloudflare myself, but my understanding is that by default they don’t cache HTML at all (they do cache images/styles/etc). That means that slow WP page-generation will slow down Cloudflare-served pages. Have you configured Cloudflare to cache HTML?
If it’s possible, you might let us know the URL of your WP site? I can think of lots of reasons why a WP site might slow down, but it is hard to know what is going on without specifics. Possibilities include:
- heavy load on shared server (check
- Change in CDN performance
- WP auto-upgrade causing problems or interacting badly with plugins
- Recent Trusty upgrade interacting badly with plugin or custom code
- WP install hacked
- heavy traffic on un-cached WP site
Just as a base benchmark, I find that a basic WP site with Super-Cache enabled can serve their blog page in ~30ms (median, first hit is longer due to DNS, etc) on Dreamhost’s shared servers. Static sites pages are about the same.
Without Super-Cache, page-generation takes 10-20 times longer, with a lot of variation. Typically 500-1500ms.
Here’s the command I run on the site’s shared server. Run several times to see median:
$ time curl -s https://blog.example.com > /dev/null