[Dave_Rosenthal]

FoundationDB's original promise was to combine a distributed storage engine with stateless layers on top to expose a variety of useful data structures (including SQL). The company was acquired before it could release the layers part of that equation. Apple open-sourced the core storage engine a few years later so FDB has kind of had a second life since then.

In that second life, the vast majority of the powerful databases around the industry built on FoundationDB have been built by companies making their own custom layers that are not public. This release is cool because it's a rare case that a company that has built a non-trivial layer on top of FDB is letting that source code be seen.

The group to which the FoundationDB storage engine itself appeals is fairly narrow--you have to want to go deep enough to build your own database/datastore, but not so deep to want to start from scratch. But, for this group, there is still nothing like FoundationDB in the industry--a distributed ACID KV store of extreme performance and robustness. So, yes, it's still the hotness in that sense. (As others have mentioned, see e.g. Deepseek's recent reveal of their 3FS distributed filesystem which relies on FDB.)

[jbverschoor]

AFAIK, the SQL layer was available and released

[Dave_Rosenthal]

There have been some 3rd party toy projects in the past years, but pretty sure nothing was ever released by FoundationDB/Apple relating to SQL (until this additional SQL interface on the Apple "record layer").