Always use a consistency level at QUOROM for both write and read operations.
Windowing doesn't work on calendar
Impacts: each cassandra requests would be longer to execute but it should be quite the same time
QA: on our production server, it is really difficult to test with "reproduction steps" as this change only fix issues about the "eventually consistent" concept, see http://www.datastax.com/documentation/cassandra/2.0/cassandra/dml/dml_config_consistency_c.html
Validated by Michel Maudet