I'm afraid I'd have to defer to the public docs on this. I've only used it internally and a bunch of that is not public.

What I would say is that it's considered to be much better than CockroachDB, but that there's no getting around physics. Spanner is subject to the same speed of light... but in every other way it does what it can do to improve things at every level. Google's use of GPS hardware for better timing is public.

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