RavenDB is a document database which claims to offer ACID transactions, including Snapshot Isolation by default and Serializability with the strongest settings. Following the documentation’s claim that a session “represents a single business transaction,” we tested RavenDB 6.0.2 and found surprising behavior even in healthy, single-node clusters. Transactions lose updates by default. Both the optimistic concurrency and cluster-wide transaction modes allow fractured read: a serious anomaly forbid...