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The answer I can find in the FAQ is as follows

An object stays in an edge location until it expires. After the object expires, CloudFront must go back to the origin server the next time that edge location needs to serve that object. By default, all objects automatically expire after 24 hours.

However, I've been noticing recently that objects seem to be getting updated much more frequently than this. I tested a text file and changed it, and within the hour it reflected the change.

I'm just not clear if this was a fluke - or if they changed the expiration rules. Is this country/region specific - or were they just doing routine maintenance at the exact hour I tested (unlikely!) ?

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2 Answers 2

The file isn’t necessarily cached on all of CloudFront’s edge servers. You may have retrieved the file from one location the first time, and a different edge server the second time.

You can see where the file is coming from by examining the Via HTTP header, which you can view by doing: curl -i http://your.url/.

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i'll check this using Fiddler. thanks for the tip. i'm in the same location with the same IP though. i'm just wondering if theyre trialing this change because a value 24 hours i'm sure is losing them a lot of customers for many applications –  Simon Jul 31 '09 at 0:09
    
Even with the same IP, your requests are likely hitting one of many different CloudFront servers at a particular AWS datacenter. –  ceejayoz Mar 19 '12 at 16:19

CF use many servers which you can test by requesting the same file a few times while you tail the access log files. Then you will notice several different IP addresses requesting the file with the CloudFront user-agent.

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