Your teammate has asked you to review the code below, which is adding a credit to an account balance in Cloud Datastore. Which improvement should you suggest your teammate make?

Question

Exhibit

Options

• AGet the entity with an ancestor query.
• BGet and put the entity in a transaction.
• CUse a strongly consistent transactional database.
• DDon't return the account entity from the function.

• A
  3% (1)
• B
  78% (28)
• C
  8% (3)
• D
  11% (4)

Explanation

https://cloud.google.com/datastore/docs/concepts/transactions#uses_for_transactions This requires a transaction because the value of balance in an entity may be updated by another user after this code fetches the object, but before it saves the modified object. Without a transaction, the user's request uses the value of balance prior to the other user's update, and the save overwrites the new value. With a transaction, the application is told about the other user's

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