+
+ # Serve stale cache on errors or if updating
+ fastcgi_cache_use_stale error timeout updating http_500 http_503 http_504;
+ # If in cache as stale, serve stale and update in background
+ fastcgi_cache_background_update on;
+ # Enable revalidation using If-Modified-Since and If-None-Match for stale items
+ fastcgi_cache_revalidate on;