Configuration for microcaching on nginx.

nginx-microcache.conf

# Setup var defaults
set $no_cache "";

# If non GET/HEAD, don't cache & mark user as uncacheable for X second(s) via cookie
if ($request_method !~ ^(GET|HEAD)$) {
   set $no_cache "1";
}

# Drop no cache cookie if need be (for some reason, add_header fails if included in prior if-block)
if ($no_cache = "1") {
   add_header Set-Cookie "_mcnc=1; Max-Age=2; Path=/";
   add_header X-Microcachable "0";
}

# Dont cache the following URLs
if ($request_uri ~* "/(admin/|ajax/)") {
   set $no_cache "1";
}

# Bypass cache if no-cache cookie is set
if ($http_cookie ~* "_mcnc") {
   set $no_cache "1";
}

# Bypass cache if flag is set
fastcgi_no_cache $no_cache;
fastcgi_cache_bypass $no_cache;

# Set cache zone
fastcgi_cache microcache;

# Set cache key to include identifying components
fastcgi_cache_key $scheme$host$request_method$request_uri;

# What, and for how long to cache
fastcgi_cache_valid 200 301 1s;
fastcgi_cache_valid 403 404 5m;

# Set files larger than 1M to stream rather than cache
fastcgi_max_temp_file_size 1M;

# Restricts the number of concurrent attempts to populate the cache
fastcgi_cache_lock on;

# Serve from cache if currently refreshing
fastcgi_cache_use_stale updating error timeout invalid_header http_500;

# Send appropriate headers through
fastcgi_pass_header Set-Cookie;
fastcgi_pass_header Cookie;
fastcgi_ignore_headers Cache-Control Expires Set-Cookie;