Spanner does guarantee consistency, thanks to its use of hardware atomic clocks and GPS. It's alternatives like CockroachDB that don't have this dedicated hardware that can fail to guarantee consistency if clocks get of sync (a problem that can't happen in Spanner).
Spanner is really fast and massively parallelizable.
Neat. The obvious question would be, how does kronos compare with ntpd? Do they work together, is kronos a replacement, do they solve different problems, etc.? Is it expected that all the servers in a cluster synced by kronos are already running ntpd, and that kronos provides an additional level of reduced skew on top of that?
It'd be great if you could address this somewhere in the top level README on GitHub.
I've added a section in the README for this.
It works in conjunction with NTPD and the time provided by this library has some extra guarantees like monotonicity, immunity to large clock jumps etc (more info in the README).
Spanner is really fast and massively parallelizable.