Like Edward says Cassandra's conflict resolution strategy is LWW (last write wins). This may seem simplistic, but Cassandra's Big Query-esque data model makes it less of an issue than in a pure key/value-store like Riak, for example. When all you have is an opaque value for a key you want to be able to do things like keeping conflicting writes so that you can resolve them later. Since Cassandra's rows aren't opaque, but more like a sorted map LWW is almost always enough. With Cassandra you can add new columns/cells to a row from multiple clients without having to worry about conflicts. It's only when multiple clients write to the same column/cell that there is an issue, but in that case you usually can (and you probably should) model your way around that.