I'm constantly surprised more folks don't use FoundationDB, I'm pretty sure the Jepsen folks said something to the tune of the way FoundationDB is tested is far beyond what Jepsen does (Good talk on FDB testing: https://www.youtube.com/watch?v=4fFDFbi3toc).
My read is that most use cases just need something that works _enough_ at scale that the product doesn't fall over and any issues introduced by such bugs can be addressed manually (i.e. through customer support, or just sufficient ad-hoc error handling). Couple that with the investment some of these databases have put into onboarding and developer-acquisition, and you have something that can be quite compelling even compared to something which is fundamentally more correct.
As someone who is switching to FoundationDB: because it's not easy. It doesn't look like other databases, it isn't in fashion (yes, these things matter), and it requires thinking and adapting your application to really use it to its full potential. It could also benefit from a bit more developer marketing.
Having looked at FoundationDB a bit it wasn't clear why I would choose it. It has transactions, which is nice, but not that big of a deal despite how much time they put into talking about it. I actually don't even need transactions since all of my writes commute, so it's particularly uninteresting to me.
They say they're fast, but I didn't find a ton of information about that.
Ultimately the sell seemed to be "nosql with transactions" and I just couldn't justify putting more time into it. I did watch their excellent talk on testing, and I respect that they've put that level of effort into it, and it was why I even considered it, but yeah, what am I missing?
My read is that most use cases just need something that works _enough_ at scale that the product doesn't fall over and any issues introduced by such bugs can be addressed manually (i.e. through customer support, or just sufficient ad-hoc error handling). Couple that with the investment some of these databases have put into onboarding and developer-acquisition, and you have something that can be quite compelling even compared to something which is fundamentally more correct.