thank you Maxim,
I ll try with your suggestions.
So basically, if I have a "production" server and a proxy server in front of it, I just need cache on the proxy server (http://nginx.org/en/docs/http/ngx_http_proxy_module.html#proxy_cache_valid) , and not cache responses on the production server?

I have this setting on production server:

# Set Cache for my Json api
location ~* \.(?:json)$ {
expires 1M;
access_log off;
add_header Cache-Control "public";
}

But if I am using a proxy server it is useless, correct?