Easiest way I found is to use an "append-only" mentality to avoid conflict entirely. So, to take the vote example, using:

  [
    {ts: <upvoted_time>, author: <id_of_author>. action: 'up'},
    {ts: <upvoted_time>, author: <id_of_author>, action: 'down'},
    {ts: <upvoted_time>, author: <id_of_author>, action: 'up'}
  ]

You can sync from the server the changes after a certain timestamp, and the client can calculate the accurate value.

That common approach is both elegant and tricky. It requires very precise clocks and time synchronization, as some non-commutative operations are order-dependent (such as list insertion).

That is why Google's TrueTime API (introduced in Spanner[0]) is such a big deal.

[0]: http://static.googleusercontent.com/external_content/untrust...

Actually, for most use cases, newest update wins is sufficient if it can be done on a fine granular basis (one property of an object/document). It's what web applications have been doing for forever and being a 'realtime' framework doesn't change this if your use case isn't something like google docs.