In an eventually consistent database, if you ask two different replicas the same question at the same time, you may get two different answers. That’s confusing. Wouldn’t it be a lot simpler if the database could give the illusion that there is only one replica (i.e., only one copy of the data)? Then every client would have the same view of the data, and you wouldn’t have to worry about replication lag. This is the idea behind linearizability [6] (also known as atomic consistency [7], strong consistency, immediate consistency, or external consistency
