I wonder why they have that there when they're actually running nginx:

  689 ~ % curl -i bit.ly/test
  HTTP/1.1 301 Moved
  Server: nginx/0.7.67

Are they using AOLServer behind nginx? That seems bizarre.

Nothing bizarre about it, given that nginx can serve many thousands of slow-receiving web clients while AOLserver usually uses 1 thread per connection - so 20 slow clients can effectively stall 20 threads.

Thus the strategy is to use nginx to serve static content like .css .js .png .jpg .gif, plus grab the dynamic content from AOLserver and buffer it out to the order of magnitude slower clients (10Mbps client vs 100Mbps or 1Gbps link between nginx and AOLserver).

Thanks for the explanation. I've never used AOLServer and was unaware of its limitations. Seems to have the same limitations/scaling problems as the two most popular Apache MPMs. :)

My main setup nowadays is HAPRoxy -> nginx load balancers -> Unicorns.