title: AWS CloudFront - When the "Regional Data Transfer Out to Origin" cost is charged?
body: <p>Sorry for my poor english.</p>
  
  <p>I'm considering using AWS CloudFront and inquiring the pricing policy from <a href="https://aws.amazon.com/cloudfront/pricing/" rel="nofollow noreferrer">https://aws.amazon.com/cloudfront/pricing/</a></p>
  
  <p>Other sections are understandable for me, but I can't understand when the "Regional Data Transfer Out to Origin" cost is charged.</p>
  
  <p>As I understood, a CDN only fetches data from origin server for caching and there is no need to transfer data out to origin server.</p>
  
  <p>Which case a CDN sends data to origin server?</p>