Nginx cache reverse proxy: how to keep app server alive during the 5 second window when cache expires?

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http://serverfault.com – I have an nginx server sitting in front of apache running django. Most of my site is static content: http://www.grovemade.com/ My app server can handle the pieces that needs to be dynamic just fine (POST, cart, order status, faq, etc.). A far far majority of hits are to static pages like product pages, about pages, ajax get requests. It handles like a champ serving pages straight out of memcached. I actually asked SF for help determining my bottleneck here: Does this prove a network bandwidth bottleneck? and it's limited by my hosts outbound traffic limiting. thus it's 100% capable for any (HowTos)