The document discusses different solutions for handling transactions at a supermarket checkout. Solution 1 proposes creating a separate transaction for each item, persisting the items with inactive status and committing after payment to set the order to active. Solution 2 keeps a long transaction open during processing, saving items without changing quantities until payment commits and updates quantities and cash amounts. Solution 3 keeps all changes in memory until a transaction at the end saves the full order to the database. Solution 4 uses pessimistic locking to serialize transactions, immediately updating the database for each item and locking concurrent transactions until commit.

1. Transactions: Case Study Svetlin Nakov National Academy for Software Development academy.devbg.org Transactions at the Supermarket’s Pay-Desk

3. Solution 1 Add Each Item in Separate Transaction

6. Solution 2 Keep Long Transaction Perform Critical Changes in the Last Moment

10. Solution 3 Disconnected Model Keep All Changes in the Memory; Small Transaction Commits All of Them at Once

13. Solution 4 Just Pessimistic Locking

15. Transactions: Case Study Questions ?