Hi, I've noticed that ci.guix.info (which I see maps to the same IP address as berlin.guixsd.org) does not return a Cache-Control header for some substitutes. I've tried various URLs under the /nar/gzip/ prefix, and and they all omitted a Cache-Control header in the response. For example: --8<---------------cut here---------------start------------->8--- $ curl --dump-header - -s -o /dev/null https://ci.guix.info/nar/gzip/0fw7w396llw316nj36dsqnbkxzc9bqwa-python-itsdangerous-0.24 HTTP/1.1 200 OK Server: nginx/1.14.1 Date: Thu, 13 Dec 2018 06:49:04 GMT Content-Type: application/octet-stream;charset=ISO-8859-1 Content-Length: 19449 Connection: keep-alive --8<---------------cut here---------------end--------------->8--- However, some URLs do include a Cache-Control header in the response. For example: --8<---------------cut here---------------start------------->8--- $ curl --dump-header - -s -o /dev/null https://ci.guix.info/s8v7vrzgpjkyf72dlbifhprabqqlx696.narinfo HTTP/1.1 200 OK Server: nginx/1.14.1 Date: Thu, 13 Dec 2018 06:49:25 GMT Content-Type: application/x-nix-narinfo;charset=utf-8 Content-Length: 1456 Connection: keep-alive Cache-Control: max-age=7776000 --8<---------------cut here---------------end--------------->8--- I expected all URLs to return an appropriate Cache-Control header (at least when returning an HTTP 200 response), especially the URLs for the gzipped substitutes themselves, since they are likely to be large. Is there a reason why we do not include a Cache-Control header for all substitutes under the /nar/gzip/ prefix? -- Chris