How does Netflix Use and Manage DNS to Improve Service?

Continuing my mini-series on "How does Netflix Manage Video Delivery?" (here, here) - and this time: how do they manage their DNS entries to allow dynamic updates?

A blog post by Adrian Cole (pictured) explains: "During 2013 we have been working on the components needed to automate DNS configuration changes. This will let us send customers to more than one region in the cloud, and switch customer traffic between cloud regions. The Denominator project provides a command line tool and a Java library that manages DNS, and can interface to several different DNS vendors". 

"..One of the options provided by some DNS vendors is called "directional routing". This looks up the location of a customer, and can automatically send customers on the west coast to a cloud region in Oregon, while sending customers on the east coast to a cloud region in Virginia. Each state can be configured separately. This feature is now supported by Denominator 1.1, which was released a few days ago. Denominator can create the configuration and dynamically switch customers from one coast to the other to balance traffic, or work around maintenance downtime and outages"

See "Denominating Multi-Region Sites" - here.