I saw Anders give this overview live at a Hubweek presentation at the Boston Fed a few months back. Excellent overview. Not sure if he's still working at Circle, but their recent pivot away from Bitcoin is a bummer - but I'm told they're still utilizing the Blockchain as an underlying technology for their systems.
Thanks for the comment - I am still with Circle, and indeed we still use the bitcoin blockchain behind the scenes. We're also working on a smart contract platform called Spark. More to come on that in a bit.