Perfect. This setting restrict Cloudflare from caching only static elements such as CSS, JS, Images, etc.
Web Tools : HTTP / HTTPS Header Check
HTTP/1.1 200 OK =>
Server => nginx/1.10.3 (Ubuntu)
Date => Sun, 10 Jun 2018 10:33:25 GMT
Content-Length => 1824
Connection => close
X-Powered-By => Express
Accept-Ranges => bytes
Cache-Control => public, max-age=0
Last-Modified => Sun, 15 Apr 2018 15:19:56 GMT
ETag => W/"720-162c9e42a43"
set-cookie => connect.sid=s%3A-4HHHyam6eW47m6lDP4VnYRBGJV1BSTo.RPJiKaea20AB53qCibGiFIw3speH2kVIiNxYXrYDDw0; Path=/; HttpOnly
It appears your origin server is instructing do no cache with max-age value 0. In this case, Cloudflare will not cache if there is settings to respect existing origin header. But you may want Cloudflare to do cache for your static files, in order of resolve this issue
- Login to Cloudflare > Select domain > Cache > Override the Browser cache time period from Respect existing header to 1 week at least.