Nginx reverse proxy cache, connecting to a static file provider

default.conf

# Declare a cache named static-cache
proxy_cache_path     /data/nginx/cache levels=1:2 keys_zone=static-cache:2m max_size=100m inactive=7d use_temp_path=off;
proxy_cache_key       $scheme$proxy_host$request_uri;
proxy_cache_lock      on;
proxy_cache_use_stale updating;

server {
  listen      80;
  server_name _;

  sendfile           on;
  sendfile_max_chunk 1m;
  keepalive_timeout  60;

  location / {
    proxy_buffering       on;
    proxy_cache           static-cache;
    proxy_cache_valid     404 1m;
    proxy_cache_use_stale error timeout updating http_404 http_500 http_502 http_503 http_504;
    proxy_cache_bypass    $http_x_purge;
    add_header            X-Cache-Status $upstream_cache_status;
    add_header X-Content-Type-Options nosniff;

    proxy_pass http://<master-server>;
  }
}