Reserved Instances mystery solved

AWS is an amazing piece of cloud, but the documentation is not always clear. I’ve been scratching my head trying to understand how Reserved Instances pricing was applied to actual instances. First I was searching for a “Launch a Reserved Instance” button, or even “Associate this Reserved Instance”, but no, nothing. I found the official documentation to be quite evasive so I took my chance on the ##aws IRC channel on irc.freenode.net; there I found a very friendly community that explained me (and many more after me) the simple truth: It’s all automagic!

In short: once you purchased a Reserved Instance, any instance that will match this RI properties will have its price set to the purchased RI. That simple.