I don't think you can ever think to a total order between events. In your example. My understanding is that the 2 events in your example happened in parallel (by redis definition of time granularity), and there's no correct ordering between the two. What I want to say is that even if you change to a ":" you'd get wrong results.

I think antirez is saying that, by serializing the id in this way, you can also get timeseries at the ms precision for free.

Edit: nvm, antirez just replied :)