Of course, there are several guarantees that HATs cannot provide. Not even the best of marketing teams can produce a real database that “beats CAP”; HATs cannot make guarantees on data recency during partitions, although, in the absence of partitions, data may not be very stale. HATs cannot be “100% ACID compliant” as they cannot guarantee serializability, yet they meet the default and sometimes maximum guarantees of many “ACID” databases. HATs cannot guarantee global integrity constraints (e.g., uniqueness constraints across data items) but can perform local checking of predicates (e.g., per-record integrity maintenance like null value checks). In the report, we classify many of these anomalies in terms of previously documented isolation levels.
HAT, not CAP: Introducing Highly Available Transactions | Peter Bailis