title: what design pattern to use for multiple throttled api requests?
body: <p>I'm writing a web site that uses multiple web services with throttle restrictions. I.e. Amazon is 1 request per second, another is 5000/day another is x/minute.</p>
  
  <p>When a user does something, I need to trigger one or more requests to the above services and return the results (to the browser) when available.</p>
  
  <p>The solution need to be flexible so I can easily add/remove services.</p>
  
  <p>I thought of a FIFO queing system, but some later requests may actually be eligible for processing before earlier ones.</p>
  
  <p>I'm asking for a design pattern, but any suitable technology suggestions are very welcome, particularly .NET.</p>
  
  <p>Thanks!</p>