FWIW, the original Dynamo concept supported safety by returning not just the latest version, but all conflicting versions: the client then had the opportunity to make a merged version of the data that was newer than either of the inputs, and store that as a replacement.

It should therefore be remembered that many/most implementations of "eventual consistency" have these issues, it is not a requirement of the mechanism, and some implementations realize this and either have merge implementations or have plans to provide them.

(I am not certain where Cassandra is on this axis, but last I paid attention they were actively trying to decide whether to modify the client protocol to match Dynamo, or provide server-assisted merge operators more similar to their existing server-assisted comparison operators.)