Like most things, it's more complex than that, and as a result it can be either faster or slower than 'median(RTT to each DC in quorum)'.

It's a delicate balance based on the locations that rows are being read and written. In the case where a row being repeatedly written from only one location and not being read from different location, the writes can be significantly faster than would be naively expected.

> Like most things, it's more complex than that,

Sure, no doubt. My point wasn't really about the particularities. It was around the mistaken idea that I see sometimes where people believe that TrueTime allows for synchronized global writes without any need for consensus.

The speed of light in vacuum is a hard upper limit. Most signal paths will be dominated by fibre optics (about 70% of C) and switching (adding more delay).

But, yes TrueTime will not magically allow data to propagate at faster-than-light speeds.

If you think people believe that Google has invented faster than light technology, either I'm overestimating people, or you're underestimating them.

With a username of azurelake though, I'm wondering: what's your real motivation for the "gentle note"? Too many lost sales to GCP because Azure Cosmos DB can't compete?

I think a Microsoft shill might choose a less suggestive name

> so they're still subject to the speed of light.

I giggled. Good witty comment, bravo.

I get the impression that you think "still subject to the speed of light" is some kind of hyperbole or something, like if you were on a freeway and saw a sign that said "end speed limit" and thought to yourself "welp, still can't go faster than c".

But when you're working on distributed systems that span the planet (say multi-master setups where ~every region can read and even write with low latency), you start thinking of the distance between your datacenters not in miles or kilometers but in milliseconds. The east coast and west coast of the US are at least 14 milliseconds apart:

  % units "2680 miles" "c ms"
  2680 miles = 14.386759 c ms

and that's not counting non-optimal routing, switching delays, or the speed of light in fiber (only 70% of c). Half of the circumference of the earth (~12500 miles) is likewise 67 milliseconds away absolute best case (unless you can somehow make fiber go through the earth).