Railsplayground / Amazon S3 authenticated_url "Gotcha"

I have been using Railsplayground for a number of years to host a few RoR applications which use S3 to store confidential documents. Due to the nature of the documents, I have been using S3’s “authenticated_url” with a 10 second timeout. About a week ago my hosted apps stopped working, even though they continued to work properly from my development machine on localhost. The problem was that the hosted server’s clock was off by about 10 seconds. When I originally asked support if the clock was off, I was told (incorrectly) that it was correct. Upon modifying my code to increase the timeout to 20 seconds, the apps returned to normal operation. Once I gave that background info to their support people they actually went in and resynced the server’s clock, so I was able to change the timeouts back to 10 seconds. The lesson… Confirm the accuracy of your server’s clock if you use S3 with authenticated_url.