Yeah I think (heard anecdotally) both google/YouTube and Facebook (and many others) started with MySQL. Spanner for distributed writes has inspired most implementations although Google is the only one I know about that implements TrueTime (atomic clocks). The same year that the Spanner paper came out (after Percolator) an alternate approach (Calvin) was also published, and some of us are using that (our DB's design is inspired by it, but we've done a lot of enhancements since then).