Hello,
   I am pretty new to Cassandra and I have some questions, they may seem trivial, but still I am pretty new to the subject. First is about the lack of a compareAndSet() operation, as I understood it is not supported currently in Cassandra, do you know of use cases which really require such operations and how these use cases currently workaround this .
Second topic I'd like to discuss a little bit more is about the read repair, as I understand is that it is being done by the timestamps supplied by the client application servers. Since computer clocks (which requires synchronization algorithms working regularly) diverge there should be a time frame during which the order of the client request written to the database is not guaranteed, do you have real world experiences with this? Is this similar to the casual consistency ( http://en.wikipedia.org/wiki/Causal_consistency ) .What happens if two application servers try to update the same data and supply one and the same timestamp (it could happen although rarely), what if they try to update several columns in batch operation this way, is there a chance that the column value could be intermixed between the two update requests?
I have one last question about the consistency level ALL, do you know of real use cases where it is required (instead of QUORUM) and why (both read and write)?
Thank you very much for your help to better understand 'Cassandra'!
Best regards, Daniel.