[h43k3r]

Lookup Google's Spanner. It's a distributed transactional SQL database with whatever consistency levels you are interested in

Disclaimer- Google employee who is heavily using Spanner

[tutfbhuf]

Yes, but Google Spanner is not open source, so it's not so easy to actually look at it. But what is known to public is that Spanner relies on perfectly synchronized atomic clocks within their datacenters, called TrueTime. This solution is very special and does not work for other databases in general.