About transactions and concurrency control
Everything in a transaction succeeds or the entire transaction is rolled back.
A transaction cannot leave the database in an inconsistent state.
Transactions cannot interfere with each other.
Completed transactions persist in the event of crashes or server failure.
As a non-relational database, Cassandra does not support joins or foreign keys, and consequently does not offer consistency in the ACID sense. For example, when moving money from account A to B the total in the accounts does not change. Cassandra supports atomicity and isolation at the row-level, but trades transactional isolation and atomicity for high availability and fast write performance. Cassandra writes are durable.