As far as I know they still store all critical data in Oracle.
(That is actually true for many user for NoSQL data bases, not just Cassandra or Netflix).
My information is a bit dated, so that might no longer be the case.
I don't know if this is heretical to say, but when I think about services that people should look up to in terms of architecture, I don't think of Netflix.
See all the downtime they have despite the 1000 posts on their blog about how wonderfully available their architecture is.
I can point to 10 other sites running on a boring LAMP stack with similar availability.
And if you examine the causes of Netflix' downtime, is it because of their usage of Cassandra? Would a LAMP service running on the same AWS ELB nodes have avoided said downtime?
You joined here two days ago. Please provide the list of these ten LAMP sites with similar scale and availability. Otherwise you just look like a troll account.
My information is a bit dated, so that might no longer be the case.