I don't see anything here that looks untoward. They increased their data storage by 3 orders of magnitude and decided to use a different DB system. Fair enough,

I don't see anything here that looks untoward. They increased their data storage by 3 orders of magnitude and decided to use a different DB system. Fair enough, maybe they've learned more about the nature of their data. But that logic isn't sound. When dealing with huge amounts of data there are going to be trade-offs. Picking a system that makes different trade-offs to an existing system is not automatically helpful. Yes you don't have the old problems. However, you are about to discover new problems. There is always something of a gamble around which will be more of a problem to your business.