Yeah google's True Time system pretty much is the only one I know of. https://cloud.google.com/spanner/docs/true-time-external-consistency https://cloud.google

Yeah google's True Time system pretty much is the only one I know of. https://cloud.google.com/spanner/docs/true-time-external-consistency https://cloud.google.com/spanner/docs/true-time-external-con...