FoundationDB is absolutely incredible and I've been wondering why it doesn't get more popular over time. I suspect it's too complex to use directly in most applications, with people used to SQL-based solutions or simple KV stores.

I always wanted my app to use a fully distributed database (for redundancy). I've been using RethinkDB in production for over 8 years now. I'm slowly rebuilding my app to use FoundationDB.

What I discovered when I started using FDB surprised me a bit. To make really good use of the database you can't really use a "database layer" and fully abstract it away from your app. Your code should be fully aware of transaction boundaries, for example. To make good use of versionstamps (an incredible feature) your code needs to be somewhat aware of them.

I think FDB is a great candidate for implementing a "user-friendly" database on top of it, and in fact several databases are doing exactly that (using FDB as a "lower layer"). But that abstracts away too much, at least for me.

The superficial take on FDB is "waah, where are my features? it doesn't do indexing? waaah, just use Postgres!".

But when you actually start mapping your app's data structures onto FDB optimally, you discover a whole new world. For example, I ended up writing my indexing code myself, in my language (Clojure). FDB gives you all the tools, and a strict serializable data model to work with — your language brings your data structures and your indexing functions. The combination is incredible. Once you define your index functions in your language, you will never want to look at SQL again. Plus, you get incredible features like versionstamps — I use them to replace RethinkDB changefeeds and implement super quick polling for recent changes.

Oh, and did I mention that it is a fully distributed database that correctly implements the strict serializable consistency model? There are very few dbs that can claim that. If you understand what that means, you probably know how incredible this is and I don't have to convince you. If you think you understand, I suggest you go and explore https://jepsen.io/consistency — carefully reading and learning about the differences in various consistency models.

I really worry that FoundationDB will not become popular because of its inherent complexity, while worse solutions (ahem, MongoDB) will be more fashionable.

I would encourage everyone to at least take a look at FDB. It really is something quite different.