Forum: NGINX Caching authentication requests?

I want to use something like auth PAM but this seems to cause a PAM
conversation for every request and that is slower.  Is there a way to 
cache
a successful authentication so that an authentication happens only once 
or
every so many seconds?

I asked this question awhile ago but got no responses.  I guess that 
means
its either majorly stupid or completely obvious.  I'm running on a
beaglebone and when I enable something like auth_pam the number of 
requests
I can handle drops from about 500 per second to about 30 which isn't
suitable.  Any kind of point would be help.

Posted at Nginx Forum: 
http://forum.nginx.org/read.php?2,233054,233534#msg-233534