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The "FAQ" page has been changed by JonathanEllis:
https://wiki.apache.org/cassandra/FAQ?action=diff&rev1=161&rev2=162

  <<Anchor(clocktie)>>
  == What happens if two updates are made with the same timestamp? ==
  
- Updates must be commutative, since they may arrive in different orders on 
different replicas.  Thus, in the case of a timestamp tie, Cassandra follows 
two rules: first, deletes take precedence over inserts/updates.  Second, if 
there are two updates, the one with the lexically larger value is selected.
+ Updates must be commutative, since they may arrive in different orders on 
different replicas.  As long as Cassandra has a deterministic way to pick the 
winner, the one selected is as valid as any other, and the specifics should be 
treated as an implementation detail.  That said, in the case of a timestamp 
tie, Cassandra follows two rules: first, deletes take precedence over 
inserts/updates.  Second, if there are two updates, the one with the lexically 
larger value is selected.
  

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