Transactions

A transaction is a way of grouping several reads and writes together. It then either:

* Succeeds (_commit_)
* Fails (_abort_, _rollback_)

ACID

• Atomicity
  • If anything happens while performing an operation, it's rolled-back so that it is then safe to retry (all-or-nothing).
• Consistency
  • It's a property of the application, which guarantees that statements about data remains true (invariants), just like in accounting credits and debuts are always balanced.
• Isolation
  • Makes clients think they are the only user of the database (no race condition)
• Durability
  • Promise that once a transaction is committed, you are sure data will remain.

Datastores with leaderless replication usually does not follow this principle. So it's the application's responsibility to recover from errors.