Apache Cassandra™ 2.0

About transactions and concurrency control

Cassandra does not use RDBMS ACID transactions with rollback or locking mechanisms, but instead offers atomic, isolated, and durable transactions with eventual/tunable consistency that lets the user decide how strong or eventual they want each transaction’s consistency to be.
  • Atomic

    Everything in a transaction succeeds or the entire transaction is rolled back.

  • Consistent

    A transaction cannot leave the database in an inconsistent state.

  • Isolated

    Transactions cannot interfere with each other.

  • Durable

    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.