I use it in production for a game that supports over 100,000 concurrent users and it's been around for a very long time.
It's fully ACID by default but you get the ability to drop elements of ACID in exchange for greater performance in a per table or transaction level. It also supports two different isolation approaches on a per table level. Locking or MVCC (like postgres).
It's a really great NoSQL database from the days before the term NoSQL existed.
https://en.wikipedia.org/wiki/Lightning_Memory-Mapped_Databa...
Still there are plenty of highly distributed stores to go around, and it's good to know that people are actively using them with great success.
It's very nice to have fine control over consistency vs performance even if you do have to think about it as a developer, but then that's our job :-)
LMDB has taken its place in a lot of projects that used to use Berkeley.
which was inspired by this paper:
http://research.google.com/archive/spanner.html
which google made available for all in form of it's cloud datastore:
https://cloud.google.com/datastore/
"We believe it is better to have application programmers deal with performance problems due to overuse of transactions as bottlenecks arise, rather than always coding around the lack of transactions." [1]
[1] http://highscalability.com/blog/2012/9/24/google-spanners-mo...
[1] http://realm.io
I haven't used it in a few years, but from what I remember you could have ACID like operations on grouped entries because grouping them makes their physical storage the same so ACID transaction becomes a localized operation.
ACID transactions
Why? In practice, people are going to be building things using the same common paths: Postgres, Mongo, MySQL, Redis, etc., and from a purely pragmatic standpoint, the SQL databases that you're likely to use come with strong ACID guarantees while the NoSQL databases don't.
If you can point me to a NoSQL data store that provides high availability, similar atomicity, consistency, and isolation properties provided by a strong isolation level in Postgres/MySQL/Oracle/SQL Server, and has a good track record of production use, I'm all ears.