Why transactions ensure atomicity in DynamoDB - Test Your Understanding

Practice - 5 Tasks

1fill in blank

easy

Complete the code to start a transaction in DynamoDB.

DynamoDB

const params = { TransactItems: [[1]] };

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A{ Put: { TableName: 'MyTable', Item: { id: '123', attribute: 'value' } } }

B{ Get: { TableName: 'MyTable', Key: { id: '123' } } }

C{ Delete: { TableName: 'MyTable', Key: { id: '123' } } }

D{ Update: { TableName: 'MyTable', Key: { id: '123' }, UpdateExpression: 'set #a = :val', ExpressionAttributeNames: { '#a': 'attribute' }, ExpressionAttributeValues: { ':val': 'newValue' } } }

Attempts:

3 left

💡 Hint

Common Mistakes

Using Get inside TransactItems which is not a write operation.

Forgetting to wrap operations inside TransactItems array.

The Put operation inside TransactItems starts a transaction to insert or replace an item atomically.

2fill in blank

medium

Complete the code to execute a transaction using DynamoDB DocumentClient.

DynamoDB

await docClient.[1](params).promise();

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AtransactWrite

Bput

Cupdate

DbatchWrite

Attempts:

3 left

💡 Hint

Common Mistakes

Using put or update which perform single operations, not transactions.

Using batchWrite which does not guarantee atomicity.

The transactWrite method executes a transaction that ensures all operations succeed or fail together.

3fill in blank

hard

Fix the error in the transaction code by choosing the correct option for the condition check.

DynamoDB

ConditionCheck: { TableName: 'MyTable', Key: { id: '123' }, ConditionExpression: '[1]' }

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Aid = :val

Battribute_exists(id)

Cattribute_not_exists(id)

Dattribute_type(id, 'S')

Attempts:

3 left

💡 Hint

Common Mistakes

Using attribute_not_exists which checks for absence, causing transaction failure.

Using invalid expressions like id = :val without defining :val.

The condition attribute_exists(id) ensures the item exists before the transaction proceeds, maintaining atomicity.

4fill in blank

hard

Fill both blanks to create a transaction that updates and deletes items atomically.

DynamoDB

const params = { TransactItems: [ { [1]: { TableName: 'Orders', Key: { orderId: '001' }, UpdateExpression: 'set #s = :new', ExpressionAttributeNames: { '#s': 'status' }, ExpressionAttributeValues: { ':new': 'shipped' } } }, { [2]: { TableName: 'Cart', Key: { cartId: 'abc' } } } ] };

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AUpdate

BPut

CDelete

DGet

Attempts:

3 left

💡 Hint

Common Mistakes

Using Put instead of Update for modifying existing items.

Using Get which is not a write operation.

The first operation is an Update to change the order status, and the second is a Delete to remove the cart item, both done atomically.

5fill in blank

hard

Fill all three blanks to define a transaction that puts, updates, and conditionally checks items atomically.

DynamoDB

const params = { TransactItems: [ { [1]: { TableName: 'Users', Item: { userId: 'u123', name: 'Alice' } } }, { [2]: { TableName: 'Profiles', Key: { profileId: 'p456' }, UpdateExpression: 'set #v = :val', ExpressionAttributeNames: { '#v': 'verified' }, ExpressionAttributeValues: { ':val': true } } }, { ConditionCheck: { TableName: 'Sessions', Key: { sessionId: 's789' }, ConditionExpression: '[3]' } } ] };

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APut

BUpdate

Cattribute_exists(sessionId)

DDelete

Attempts:

3 left

💡 Hint

Common Mistakes

Using Delete instead of Put for adding items.

Using a wrong condition expression that does not check attribute existence.

The transaction puts a new user, updates a profile, and conditionally checks if a session exists before proceeding, ensuring atomicity.