CAP extended: if partitioned, choose availability or consistency; else, even with no partition, choose latency or consistency.
the two-minute refresher
P → A or C (that is CAP); E (else) → L or C.
Keeping replicas in sync costs round trips even when the network is healthy.
Cassandra and the Dynamo design are PA/EL (fast and available, eventually consistent); the managed DynamoDB service is sometimes classed PA/EC because it offers strongly consistent reads; HBase is PC/EC.