Transactions

• Coordinated all or nothing operations (update/delete/add) to multiple items across one or more tables.

• This provides ACID guarantees.

• There are 3 read modes

  • Eventual Consistency

  • Strong Consistency

  • Transactional

• There are 2 write modes

  • Standard

  • Transactional

• It consumes twice the WCU and RCU. This is because DynamoDB performs 2 operations for every item (prepare and commit).

• The two operations are

  • TransactGetItems → To do one or more GetItem operations.

  • TransactWriteItems → To do one or more PutItem, UpdateItem and DeleteItem operations.

• Use cases includes financial transactions, managing orders, multiplayer games etc.

Transacional Capacity Computation

• To calculate transaction write capacity WCU the formula is,

      (Number of transactions) * (Item-size/1 KB) * 2 * (transactional cost)

• To calculate transaction read capacity RCU the formula is,

      (Number of transactions) * (Item-size rounded to upper factor of 4/4 KB) * 2 * (transactional cost)