Google cloud CDN backend service load balancer not caching any resources - google-cloud-platform

Question

We have a requirement to generate images on the fly and cache using CDN. For this we have configured a backend service with a load balancer enabled cloud CDN. We are using Nginx proxy server. We have added headers specified in the Google cloud CDN docs, but unfortunately it is not caching.
Request:
GET /resize?size=l&url=https://example.com/image.jpeg HTTP/1.1
Host: resize.example.com
Request Headers:
Host: resize.example.com
User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.15; rv:70.0) Gecko/20100101 Firefox/70.0
Accept: text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8
Accept-Language: en-US,en;q=0.5
Accept-Encoding: gzip, deflate
Connection: keep-alive
Upgrade-Insecure-Requests: 1
Response headers:
HTTP/1.1 200 OK
Server: nginx/1.17.2
Date: Wed, 15 Jan 2020 15:01:14 GMT
Content-Type: image/jpeg
Content-Length: 62771
cache-control: max-age=86400, public, s-maxage=86400
Via: 1.1 google

Answer 1

I suggest you a couple of pages that could help you.
a) Not all HTTP responses are cacheable. Cloud CDN caches only those responses that meet all the requirements in this section. Some of these requirements are specified by RFC 7234, and others are specific to Cloud CDN.
Cacheability for HTTP responses
Responses aren't being cached--Troubleshooting
The following example demonstrates using curl to check the HTTP response headers for http://example.com/style.css:
$ curl -s -D - -o /dev/null http://example.com/style.css
HTTP/1.1 200 OK
Date: Tue, 16 Feb 2016 12:00:00 GMT
Content-Type: text/css
Content-Length: 1977
Via: 1.1 google
Although perhaps because of the added response, you may have already read it.