Gotcha. Thanks Marcus, that makes perfect sense.
In regard to echo_location_async, I'm assuming it would allow something like so?

[code]
location /first {
echo "before";
echo_location_aysnc /second$request_uri;
echo "after"
}

location /second(.*)\?(.*)^ {
set $memcached_key $1; # needing this to be keyed on the request_path, not the entire uri
memcached_pass 127.0.0.1;
}
[/code]

That doesn't seem to work, and am not able to extrapolate the request path out of there.

The other concern is that if I was to patch the before/after echo methods, if they would be
returned in the response even if there was no valid body being passed back? For example:

[code]
location /first {
echo_before_body -n "before";
echo_location_aysnc /null; # this returns nothing
echo_after_body -n "after"
}
[/code]

In the above scenario, I think I'd have a response of "before after", even if the async call returned an empty response.
Think I'm slowly getting there, and just need to make sure I'm picking the correct route :)
Thanks!