Comment by timf

> The main reason we can not use system clocks is that system clocks across servers are not guaranteed to be synchronized.

Data center/cloud system clocks can be tightly synchronized now in practice. Still never perfect and race conditions abound.

But that doesn't mean you can't rely on a clock to determine ordering, Google popularized a different approach with TrueTime/Spanner: https://cloud.google.com/spanner/docs/true-time-external-con...