Return values on write in DynamoDB - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ query_result

intermediate

What does ReturnValues: "ALL_OLD" return on a PutItem?

You perform a PutItem operation with ReturnValues set to "ALL_OLD". What will the response contain if the item did not exist before?

DynamoDB

PutItem({ TableName: "Users", Item: { UserId: "123", Name: "Alice" }, ReturnValues: "ALL_OLD" })

A The primary key attributes only

B An empty object because no previous item existed

C An error because <code>ALL_OLD</code> is invalid for <code>PutItem</code>

D The newly inserted item attributes

💡 Hint

Think about what ALL_OLD means when no item was replaced.

When ReturnValues is set to ALL_OLD in a PutItem, DynamoDB returns the old item attributes if the item existed. If the item did not exist, the response is empty.

❓ query_result

intermediate

What does ReturnValues: "UPDATED_NEW" return on an UpdateItem?

You run an UpdateItem with ReturnValues set to "UPDATED_NEW". What will the response contain?

DynamoDB

UpdateItem({ TableName: "Products", Key: { Id: "p1" }, UpdateExpression: "SET Price = :p", ExpressionAttributeValues: { ":p": 20 }, ReturnValues: "UPDATED_NEW" })

A All attributes of the item after the update

B All attributes of the item before the update

C Only the attributes that were updated with their new values

D No attributes, just a success status

💡 Hint

Focus on what UPDATED_NEW means in the context of updated attributes.

UPDATED_NEW returns only the attributes that were changed by the update, with their new values.

📝 Syntax

advanced

Which ReturnValues option is invalid for DeleteItem?

Select the ReturnValues option that will cause a syntax or runtime error when used with DeleteItem.

DynamoDB

DeleteItem({ TableName: "Orders", Key: { OrderId: "o123" }, ReturnValues: ? })

A "ALL_OLD"

B "ALL_NEW"

C "NONE"

D "UPDATED_NEW"

💡 Hint

Consider which return values make sense for a delete operation.

UPDATED_NEW is invalid for DeleteItem because no attributes are updated during deletion.

🧠 Conceptual

advanced

Why use ReturnValues: "ALL_NEW" in UpdateItem?

What is the main reason to set ReturnValues to "ALL_NEW" when updating an item?

A To get the entire item as it looks after the update

B To get only the attributes that were updated

C To get the item as it was before the update

D To prevent the update from happening if the item exists

💡 Hint

Think about when you want to see the full updated item.

ALL_NEW returns the entire item after the update, useful to confirm all changes.

🔧 Debug

expert

Why does this UpdateItem with ReturnValues: "ALL_OLD" return empty?

You run this UpdateItem on a non-existing item with ReturnValues set to "ALL_OLD". Why is the returned attribute map empty?

DynamoDB

UpdateItem({ TableName: "Inventory", Key: { ItemId: "i999" }, UpdateExpression: "SET Stock = :s", ExpressionAttributeValues: { ":s": 10 }, ReturnValues: "ALL_OLD" })

A Because the item did not exist before, so no old attributes to return

B Because <code>ALL_OLD</code> only returns updated attributes, and none were updated

C Because <code>ReturnValues</code> is ignored on <code>UpdateItem</code>

D Because the update failed silently without error

💡 Hint

Consider what ALL_OLD means when the item is new.

ALL_OLD returns the item attributes before the update. If the item did not exist, there are no old attributes to return, so the response is empty.