Timestamp based reconciliation: This case differs from the previous one only in the reconciliation mechanism. In case of divergent versions, Dynamo performs simple timestamp based reconciliation logic of “last write wins”; i.e., the object with the largest physical timestamp value is chosen as the correct version. The service that maintains customer’s session information is a good example of a service that uses this mode.
http://www.allthingsdistributed.com/files/amazon-dynamo-sosp2007.pdf
Timestamp based reconciliation