FoundationDB was the proto-CockroachDB (or rather, CockroachDB is essentially a re-attempt at building FoundationDB). It was an early attempt at building a NewSQL database. (NewSQL per se, i.e. not counting parallel databases from the pre-NoSQL age, like Gamma [1], Volcano [2] and Grace [3], which share many of the same design principles.)

FoundationDB was acquhired by Apple, but its failure is generally attributed to a poorly-performing SQL layer: https://www.voltdb.com/blog/2015/04/01/foundationdbs-lesson-...

[1] http://pages.cs.wisc.edu/~dewitt/includes/paralleldb/ieee90....

[2] https://paperhub.s3.amazonaws.com/dace52a42c07f7f8348b08dc2b...

[3] https://pdfs.semanticscholar.org/a7f4/e4e6166dc683e7fa7d5b9e...