Idempotency tokens in DynamoDB - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to add an idempotency token attribute named 'IdempotencyKey' to the DynamoDB item.

DynamoDB

item = { 'OrderId': '123', 'Amount': 100, 'IdempotencyKey': [1] }

Drag options to blanks, or click blank then click option'

ATrue

B12345

CNone

D'unique-token-123'

Attempts:

3 left

💡 Hint

Common Mistakes

Using a number instead of a string for the token.

Using None or boolean values as tokens.

The idempotency token should be a unique string to identify the request. Here, 'unique-token-123' is a valid string token.

2fill in blank

medium

Complete the code to include the idempotency token in the DynamoDB PutItem request condition expression to prevent duplicate writes.

DynamoDB

response = table.put_item(Item=item, ConditionExpression='attribute_not_exists([1])')

Drag options to blanks, or click blank then click option'

AOrderId

BIdempotencyKey

CAmount

DTimestamp

Attempts:

3 left

💡 Hint

Common Mistakes

Checking attribute_not_exists on the wrong attribute.

Using attribute names that are not part of the item.

The ConditionExpression uses 'attribute_not_exists' on the 'IdempotencyKey' to ensure the item is only inserted if the token is not already present.

3fill in blank

hard

Fix the error in the code by completing the parameter to generate a unique idempotency token using Python's uuid module.

DynamoDB

import uuid
idempotency_token = [1]

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Auuid.uuid4()

Buuid.generate()

Cuuid4()

Duuid.random()

Attempts:

3 left

💡 Hint

Common Mistakes

Calling uuid4() without the uuid prefix.

Using non-existent methods like generate() or random().

The correct way to generate a unique UUID token is by calling uuid.uuid4().

4fill in blank

hard

Fill both blanks to complete the DynamoDB update expression that sets the idempotency token only if it does not already exist.

DynamoDB

response = table.update_item(
  Key={'OrderId': '123'},
  UpdateExpression='SET [1] = :token',
  ConditionExpression='attribute_not_exists([2])',
  ExpressionAttributeValues={':token': idempotency_token}
)

Drag options to blanks, or click blank then click option'

AIdempotencyKey

BOrderId

CAmount

DTimestamp

Attempts:

3 left

💡 Hint

Common Mistakes

Using different attribute names in UpdateExpression and ConditionExpression.

Using attributes unrelated to the idempotency token.

Both the UpdateExpression and ConditionExpression must refer to the 'IdempotencyKey' attribute to ensure the token is set only if it does not exist.

5fill in blank

hard

Fill all three blanks to complete the Python dictionary comprehension that creates a map of order IDs to their idempotency tokens, filtering only orders with tokens present.

DynamoDB

idempotency_map = {order['[1]']: order['[2]'] for order in orders if '[3]' in order}

Drag options to blanks, or click blank then click option'

AOrderId

BIdempotencyKey

DAmount

Attempts:

3 left

💡 Hint

Common Mistakes

Using the wrong attribute names for keys or values.

Filtering on an attribute not related to the token.

The dictionary maps each 'OrderId' to its 'IdempotencyKey', including only orders that have the 'IdempotencyKey' attribute.