Return values on write in DynamoDB - Step-by-Step Execution

Concept Flow - Return values on write

Start Write Operation

↓

Perform Write (Put/Update/Delete)

↓

Check ReturnValues Parameter

↓

NONE

↓

Return No

↓

Attributes

↓

End Write Operation

When you write data, you can choose what old or new attribute values to get back by setting ReturnValues.

Execution Sample

DynamoDB

UpdateItem {
  Key: {id: 1},
  UpdateExpression: 'SET age = :newAge',
  ExpressionAttributeValues: {':newAge': 30},
  ReturnValues: 'UPDATED_OLD'
}

This updates the age attribute and returns the old age value before update.

Execution Table

Step	Action	ReturnValues	Returned Data
1	Start UpdateItem	N/A	No data returned yet
2	Apply UpdateExpression	UPDATED_OLD	Old attribute values before update
3	Return response	UPDATED_OLD	{"age": 25}
4	End operation	N/A	Update complete, returned old age

💡 Update applied and old attribute values returned as per ReturnValues = UPDATED_OLD

Variable Tracker

Variable	Start	After Step 2	After Step 3	Final
age	25	30 (updated)	25 (returned)	30 (stored)
ReturnValues	N/A	UPDATED_OLD	UPDATED_OLD	UPDATED_OLD

Key Moments - 2 Insights

Why do we get old attribute values back instead of new ones?

Because ReturnValues is set to UPDATED_OLD, DynamoDB returns the attribute values before the update, as shown in execution_table step 3.

What happens if ReturnValues is NONE?

No attribute values are returned after the write, so the response contains no data, unlike the UPDATED_OLD case in step 3.

Visual Quiz - 3 Questions

Look at the execution_table, what is returned at step 3?

A The new attribute values after update

B The old attribute values before update

C No attribute values

D An error message

💡 Hint

Check the 'Returned Data' column at step 3 in execution_table

At which step is the update applied to the attribute 'age'?

A Step 2

B Step 1

C Step 3

D Step 4

💡 Hint

Look at the 'Action' column in execution_table where update happens

If ReturnValues was set to NONE, what would change in the execution_table?

A Returned Data at step 3 would show old values

B Returned Data at step 3 would show new values

C Returned Data at step 3 would be empty

D The update would not happen

💡 Hint

ReturnValues NONE means no data returned after write

Concept Snapshot

ReturnValues controls what data DynamoDB returns after a write.
Options include NONE (no data), ALL_OLD (all old attributes), UPDATED_OLD (only updated old attributes), ALL_NEW (all new attributes), UPDATED_NEW (only updated new attributes).
Set ReturnValues in your write request to get desired feedback.
Useful for confirming changes or retrieving previous data.

Full Transcript

When you perform a write operation in DynamoDB, such as UpdateItem, you can specify the ReturnValues parameter to control what attribute data is returned. The options include NONE, ALL_OLD, UPDATED_OLD, ALL_NEW, and UPDATED_NEW. For example, if you set ReturnValues to UPDATED_OLD, DynamoDB returns only the attribute values that were updated, but before the update. The execution flow starts with the write request, applies the update, checks the ReturnValues setting, and returns the requested data. This helps you confirm what changed or retrieve previous values without a separate read. If ReturnValues is NONE, no attribute data is returned. Understanding this helps you write efficient and clear DynamoDB operations.

Practice

1. What does the ReturnValues parameter do in a DynamoDB write operation?

easy

A. It specifies what data should be returned after the write operation.

B. It controls the write capacity units consumed by the operation.

C. It sets the timeout duration for the write request.

D. It defines the table where data will be written.

Solution

1. Step 1: Understand the role of ReturnValues

   The ReturnValues parameter tells DynamoDB what data to send back after a write, such as old or new item attributes.

2. Step 2: Differentiate from other parameters

   ReturnValues does not affect capacity, timeout, or table selection; it only controls returned data.

3. Final Answer:

   It specifies what data should be returned after the write operation. -> Option A

4. Quick Check:

   ReturnValues controls returned data [OK]

Hint: ReturnValues returns data after write, not capacity or timeout [OK]

Common Mistakes:

• Confusing ReturnValues with capacity settings
• Thinking it sets request timeout
• Assuming it selects the table

2. Which of the following is the correct syntax to request the old item attributes after an update in DynamoDB using ReturnValues?

easy

A. "UPDATED_NEW"

B. "NONE"

C. "ALL_NEW"

D. "ALL_OLD"

Solution

1. Step 1: Recall ReturnValues options

   ReturnValues can be NONE, ALL_OLD, UPDATED_OLD, ALL_NEW, UPDATED_NEW.

2. Step 2: Identify option for old attributes after update

   "ALL_OLD" returns the entire item as it was before the update.

3. Final Answer:

   "ALL_OLD" -> Option D

4. Quick Check:

   Old attributes = ALL_OLD [OK]

Hint: Old data after update is ALL_OLD [OK]

Common Mistakes:

• Using ALL_NEW to get old data
• Confusing UPDATED_NEW with old data
• Setting NONE expecting data back

3. Given this DynamoDB update command snippet:

{
  TableName: "Users",
  Key: { "UserId": "123" },
  UpdateExpression: "SET Age = :newAge",
  ExpressionAttributeValues: { ":newAge": 30 },
  ReturnValues: "UPDATED_NEW"
}

What will the response contain?

medium

A. The entire item before the update.

B. Only the new Age attribute after the update.

C. No attributes, just success confirmation.

D. The entire item after the update.

Solution

1. Step 1: Understand ReturnValues "UPDATED_NEW" meaning

   This option returns only the attributes that were updated with their new values.

2. Step 2: Apply to given update

   The update changes Age to 30, so response includes only Age with value 30.

3. Final Answer:

   Only the new Age attribute after the update. -> Option B

4. Quick Check:

   UPDATED_NEW returns updated attributes [OK]

Hint: UPDATED_NEW returns only changed attributes with new values [OK]

Common Mistakes:

• Expecting full item back with UPDATED_NEW
• Confusing UPDATED_NEW with ALL_NEW
• Assuming no data returned with UPDATED_NEW

4. You wrote this DynamoDB PutItem request:

{
  TableName: "Products",
  Item: { "Id": "001", "Name": "Pen" },
  ReturnValues: "UPDATED_OLD"
}

But you get an error. What is wrong?

medium

A. ReturnValues must be set to "ALL_NEW" for PutItem.

B. The Item attribute is missing required keys.

C. "UPDATED_OLD" is invalid for PutItem operations.

D. TableName is incorrect.

Solution

1. Step 1: Check ReturnValues compatibility with PutItem

   PutItem supports only NONE or ALL_OLD for ReturnValues; UPDATED_OLD is invalid.

2. Step 2: Confirm other parameters

   Item and TableName are correct; error is due to invalid ReturnValues.

3. Final Answer:

   "UPDATED_OLD" is invalid for PutItem operations. -> Option C

4. Quick Check:

   PutItem supports NONE or ALL_OLD only [OK]

Hint: PutItem allows NONE or ALL_OLD only for ReturnValues [OK]

Common Mistakes:

• Using UPDATED_OLD with PutItem
• Assuming ALL_NEW required for PutItem
• Mistaking missing keys as cause

5. You want to update a user's email in DynamoDB and get back the entire updated item in one request. Which ReturnValues option should you use in your UpdateItem call?

hard

A. "ALL_NEW"

B. "UPDATED_OLD"

C. "NONE"

D. "ALL_OLD"

Solution

1. Step 1: Understand the goal

   You want the full updated item returned after the update.

2. Step 2: Match ReturnValues option

   "ALL_NEW" returns the entire item as it looks after the update.

3. Final Answer:

   "ALL_NEW" -> Option A

4. Quick Check:

   Full updated item = ALL_NEW [OK]

Hint: Use ALL_NEW to get full updated item after update [OK]

Common Mistakes:

• Choosing UPDATED_OLD which returns old updated attributes
• Using NONE expecting data back
• Selecting ALL_OLD which returns old full item