https://discovery.hgdata.com/product/foundationdb

This "Who is hiring" post for Tesla mentions FoundationDB [0].

Firebolt [1] uses it.

FoundationDB is used at Datadog [2].

[0] https://news.ycombinator.com/item?id=26306170

[1] https://www.firebolt.io/blog/decomposing-firebolt-transactio...

[2] https://news.ycombinator.com/item?id=36576775