I have recently run into an issue after switching to Cloudflare, and the solution is to basically stop Cloudflare from caching 404 responses.
In our load-balanced multi-server setup, occasional 404s happen, but they're quickly fixed by rsync (via lsyncd). Before Cloudflare, a re-request to the 404ed file would very quickly become 200 as rsync does its job.
However, since Cloudflare caches all data based on the caching header, and neither apache nor nginx send a no-cache header for 404s, Cloudflare ends up caching the 404 response for a while.
I've been searching for a solution to globally add such a header for 404s in both apache and nginx (globally, for all hosted domains), but so far have come up blank.
Can anyone help?