Just because human lives aren't necessarily at stake it doesn't mean that poor (in my opinion) software system designs should be tolerated. And when we talk ab

Just because human lives aren't necessarily at stake it doesn't mean that poor (in my opinion) software system designs should be tolerated. And when we talk about "relational databases", we basically never mean MySQL. I'm not even sure why you'd bother to bring it up, given its poor reputation, its lack of proper functionality in some cases, and the many other (and far better) alternatives. As for scalability, some other commenter here posted a link to a twitter comment describing the scale in this case: https://twitter.com/dN0t/status/360119871318659074 https://twitter.com/dN0t/status/360119871318659074 It clearly states "tens of thousands" of transactions per second. That is well within the capabilities of the lower-end database systems on modern, low-end server hardware. Twilio will require a huge amount of growth just to reach the point where higher end database systems and hardware become appropriate, never mind "a scale that is going to continue to reach further than many traditional models will scale". Running into significant billing issues due to a likely unnecessary use (in my opinion) of a NoSQL database while still at a relatively small scale is not something that a team should be commended for, and nobody should be "thankful" that the incident did happen.