Foundation DB http://techcrunch.com/2015/03/24/apple-acquires-durable-data... "Apple has acquired FoundationDB, a company that specializes in speedy, durable NoSQL databases, TechCrunch has learned.

A notice on the FoundationDB site notes that it’s no longer offering downloads of its database software. "

Granted, Apple doesn't acquire at Google's or Facebook's rate, so the sample size is smaller