With Cassandra if you wrote at quorum and it was successful and you read at quorum you will get your value back. Where it gets hairy is when a write fails (e.g

With Cassandra if you wrote at quorum and it was successful and you read at quorum you will get your value back. Where it gets hairy is when a write fails (e.g. only one replica got it) or if writes so close to each other that the clocks are a problem. It is definitely non-trivial to build systems over that but then it's non-trivial to build systems that scale horizontally, and geographically, and are highly available, and can recover from failure, in the first place. Like the article implies, what tends to happen is people don't understand the guarantees and build software that works except when it doesn't. Then you build on top of that etc.