I'll admit I'm confused about picking Cassandra as well, but not for the same reasons you are. They're only storing subscriber data (billing address, subscription type, etc). That data is going to remain static for months at a time. When changed the only potential problem that could occur is the billing process using old data, but I'm guessing their system is smart enough to try again in thirty minutes.
Oracle may be fast, but it's also expensive. This is billing, which means batched jobs running in the background- they don't care how long each individual transaction takes, and I'm positive it's going to be cheaper to roll up more servers to compensate than it is to pay Oracle's licensing fees.
Sorry about the c/p but I don't see a permalink on lapitopi's comment.
lapitopi 1 day ago I work on the Netflix Billing Team. PostgreSQL was indeed a very attractive option, but we wanted to keep a path to Aurora open. When we were working on the migration, Aurora was still in beta, so instead of going to Aurora directly, we decided run our own MySQL instances on EC2.
edit: begun/began
Do you have any sources for the corruption comparison between Aurora vs InnoDB?
So? That's capitalism: one gets what one pays for, and Oracle is not just fast, it can do a lot, and it can be configured to be paranoid about protecting data, and it has clustering technology meant for scaling, RAC.
Truth be told they could have picked PostreSQL and it would have still been a better solution than Cassandra and MySQL.
Considering that Cassandra is not ACID compliant with her "eventual consistency", and that MySQL is notorious for corrupting data and not functioning correctly, I am compelled to wonder just what kind of people work at Netflix. And who gets the idea to go to AWS and pay the full virtualization on Linux performance penalty?
Now, I've done Oracle engineering at some very large databases (hundreds of millions of rows, OLTP and DWH), and I know that Oracle is a smoking fast database when the right people develop on it. Also makes me wonder what kind of code they had running, and what kind of people selected it, when they managed to gum up what is essentially the Bugatti Veyron of databases.
Given this information from "Netflix" I won't be considering them as a potential employer any time soon. It has to be a mess over there.