Try FoundationDB it's a distributed ACID key value store, can have databases scale up to 100TB, scales horizontally, and can handle an enormous amount of concurrent writes and reads while maintaining relatively low latency per read/write.
You can even use the Foundation Document Layer which is API compatible with Mongo.
It definitely takes some getting used to, but I think it's pretty fucking great, once you do.
Yeah, I was super excited when FoundationDB was made Open Source, but since then I haven't really heard anything about it or anyone using it in production, even less so with the Document-DB layer (Mongo). Any experiences you'd like to share?
I love it personally. I think right now those who are using it are using it as their secret sauce. Its essentially what people want from BigTable or one of the other proprietary offerings from the cloud providers, except actually open and free.
I think the biggest reason for a lack of noise about it, is the overhead of learning it is pretty high. You're not going to find folks writing their first "Nodejs + Express" applications using it. Additionally, you really have to know why most distributed databases suck ass to know why FoundationDB is so good.
Example: I have a cluster of three VMs running FDB on my home server, and over the past week I've accidentally hit the power switch three or four times. At no point did I have data loss in the cluster, the cluster "immediately" comes back up, and is ready to go. Adding machines to the cluster is unbelievably easy, especially if you have ever even tried grokking how to horizontally scale PSQL.
I'm close to releasing an Elixir-based Entity Layer which is pretty uhhh, ~~shitty~~ lacking, at this point feature wise, but it does make storing structured data a bit easier. I'm hoping it'll be more useful for helping people learn how to use FoundationDB than something folks are putting into production (though I'm dog-fooding it).
You can even use the Foundation Document Layer which is API compatible with Mongo.
It definitely takes some getting used to, but I think it's pretty fucking great, once you do.