TransactWriteItems in DynamoDB - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to start a transaction write with multiple operations.

DynamoDB

response = client.transact_write_items(TransactItems=[1])

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

A{'Put': {'TableName': 'MyTable', 'Item': {'Id': {'S': '123'}}}}

BNone

C['Put', 'Update']

D[{'Put': {'TableName': 'MyTable', 'Item': {'Id': {'S': '123'}}}}]

Attempts:

3 left

💡 Hint

Common Mistakes

Passing a single dictionary instead of a list.

Using a list of strings instead of dictionaries.

The TransactItems parameter requires a list of action dictionaries. Option D correctly provides a list with a Put operation.

2fill in blank

medium

Complete the code to add a condition expression to a Put operation in TransactWriteItems.

DynamoDB

TransactItems=[{'Put': {'TableName': 'MyTable', 'Item': {'Id': {'S': '123'}}, 'ConditionExpression': [1]]

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

A"attribute_exists(Name)"

B"Id = 123"

C"attribute_not_exists(Id)"

D"Id > 100"

Attempts:

3 left

💡 Hint

Common Mistakes

Using a condition that checks for attribute existence instead of non-existence.

Using invalid syntax for the condition expression.

The ConditionExpression "attribute_not_exists(Id)" ensures the item does not already exist before putting it.

3fill in blank

hard

Fix the error in the TransactWriteItems call by completing the missing parameter.

DynamoDB

client.transact_write_items(TransactItems=[1])

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

A[{'Delete': {'TableName': 'MyTable', 'Key': {'Id': {'S': '123'}}}}]

B[{'Delete': {'Key': {'Id': {'S': '123'}}}}]

C[{'Delete': {'TableName': 'MyTable'}}]

D[{'Delete': {'TableName': 'MyTable', 'Key': {}}}]

Attempts:

3 left

💡 Hint

Common Mistakes

Omitting the Key parameter.

Providing an empty Key dictionary.

The Delete operation requires both TableName and Key to specify which item to delete.

4fill in blank

hard

Fill both blanks to create a transaction with a Put and an Update operation.

DynamoDB

TransactItems=[{'Put': {'TableName': [1], 'Item': {'Id': {'S': '001'}}}}, {'Update': {'TableName': [2], 'Key': {'Id': {'S': '002'}}, 'UpdateExpression': 'SET #n = :val', 'ExpressionAttributeNames': {'#n': 'Name'}, 'ExpressionAttributeValues': {':val': {'S': 'NewName'}}}}]

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

A'Users'

B'Orders'

C'Products'

D'Inventory'

Attempts:

3 left

💡 Hint

Common Mistakes

Using the same table name for both operations when different tables are intended.

Omitting quotes around table names.

The Put operation targets the 'Users' table and the Update operation targets the 'Orders' table as specified.

5fill in blank

hard

Fill all three blanks to create a transaction with Put, Update, and Delete operations with conditions.

DynamoDB

TransactItems=[{'Put': {'TableName': [1], 'Item': {'Id': {'S': '100'}}}}, {'Update': {'TableName': [2], 'Key': {'Id': {'S': '101'}}, 'UpdateExpression': 'SET Age = :age', 'ExpressionAttributeValues': {':age': {'N': '30'}}, 'ConditionExpression': [3], {'Delete': {'TableName': 'Logs', 'Key': {'LogId': {'S': 'log123'}}}}]

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

A'Customers'

B'Employees'

C"attribute_exists(Age)"

D"attribute_not_exists(Age)"

Attempts:

3 left

💡 Hint

Common Mistakes

Using attribute_not_exists in the Update condition when attribute_exists is required.

Mixing up table names between operations.

The Put operation inserts into 'Customers', the Update modifies 'Employees' with a condition that 'Age' exists.

Practice

1. What is the main purpose of TransactWriteItems in DynamoDB?

easy

A. To group multiple write operations into a single atomic transaction

B. To read multiple items from different tables at once

C. To create a backup of the database automatically

D. To perform batch deletes without conditions

Solution

1. Step 1: Understand the role of TransactWriteItems

   TransactWriteItems groups multiple write actions (Put, Update, Delete) into one atomic transaction.

2. Step 2: Compare with other options

   It does not perform reads, backups, or unconditional batch deletes.

3. Final Answer:

   To group multiple write operations into a single atomic transaction -> Option A

4. Quick Check:

   Atomic transaction = group writes together [OK]

Hint: Remember: TransactWriteItems groups writes atomically [OK]

Common Mistakes:

• Confusing TransactWriteItems with batch read operations
• Thinking it automatically backs up data
• Assuming it only deletes items

2. Which of the following is the correct syntax structure for a TransactWriteItems request in DynamoDB?

easy

A. { TransactWriteItems: [{ Get: { TableName: 'MyTable', Key: {...} } }] }

B. { BatchWriteItems: [{ PutRequest: {...} }, { DeleteRequest: {...} }] }

C. { TransactItems: [{ Put: { TableName: 'MyTable', Item: {...} } }, { Update: {...} }] }

D. { WriteItems: [{ Put: {...} }, { Update: {...} }] }

Solution

1. Step 1: Identify correct TransactWriteItems syntax

   The correct syntax uses the key 'TransactItems' with an array of actions like Put and Update.

2. Step 2: Eliminate incorrect options

   BatchWriteItems is a different API; Get is not a write action; WriteItems is not a valid key.

3. Final Answer:

   { TransactItems: [{ Put: { TableName: 'MyTable', Item: {...} } }, { Update: {...} }] } -> Option C

4. Quick Check:

   TransactItems with Put/Update = correct syntax [OK]

Hint: Look for 'TransactItems' key with write actions inside [OK]

Common Mistakes:

• Using BatchWriteItems instead of TransactWriteItems
• Including Get operations inside TransactWriteItems
• Using incorrect key names like WriteItems

3. Given the following TransactWriteItems request, what will happen if the condition in the Update action fails?

{
  TransactItems: [
    { Put: { TableName: 'Users', Item: { UserId: '123', Name: 'Alice' } } },
    { Update: { TableName: 'Users', Key: { UserId: '123' }, UpdateExpression: 'SET Age = :age', ConditionExpression: 'attribute_exists(UserId)', ExpressionAttributeValues: { ':age': 30 } } }
  ]
}

medium

A. Put action succeeds; Update action is skipped

B. Both actions succeed regardless of the condition

C. Update action succeeds; Put action is skipped

D. Both Put and Update actions are rolled back; no changes are applied

Solution

1. Step 1: Understand TransactWriteItems atomicity

   All actions in TransactWriteItems succeed or all fail together as one transaction.

2. Step 2: Analyze condition failure effect

   If the Update's condition fails, the entire transaction rolls back, including the Put.

3. Final Answer:

   Both Put and Update actions are rolled back; no changes are applied -> Option D

4. Quick Check:

   Condition failure rolls back entire transaction [OK]

Hint: If any condition fails, whole TransactWriteItems rolls back [OK]

Common Mistakes:

• Assuming partial success when condition fails
• Thinking Put action always succeeds
• Ignoring atomicity of TransactWriteItems

4. You wrote this TransactWriteItems request but it fails with a syntax error:

{
  TransactItems: [
    { Put: { TableName: 'Orders', Item: { OrderId: '001', Status: 'Pending' } } },
    { Delete: { TableName: 'Orders', Key: { OrderId: '002' } } }
  ],
  ReturnConsumedCapacity: 'TOTAL'
}

What is the likely cause of the error?

medium

A. Delete action requires a ConditionExpression

B. Missing comma after the TransactItems array

C. TransactItems must be an object, not an array

D. TableName cannot be specified inside Put or Delete actions

Solution

1. Step 1: Check JSON syntax in the request

   ReturnConsumedCapacity is a valid parameter, but the JSON is invalid due to a missing comma after the closing bracket (]) of the TransactItems array.

2. Step 2: Validate other parts

   Delete and Put actions are correctly structured; TransactItems must be an array; TableName is required inside actions.

3. Final Answer:

   Missing comma after the TransactItems array -> Option B

4. Quick Check:

   JSON requires commas between object properties [OK]

Hint: Validate JSON syntax: add commas between top-level properties [OK]

Common Mistakes:

• Omitting commas in JSON request objects
• Forgetting TableName inside each action
• Misusing array vs object for TransactItems

5. You want to atomically update a user's email and delete a related temporary token in DynamoDB using TransactWriteItems. Which of the following request structures correctly achieves this?

hard

A. { TransactItems: [ { Update: { TableName: 'Users', Key: { UserId: 'u1' }, UpdateExpression: 'SET Email = :e', ExpressionAttributeValues: { ':e': '[e-mail]' } } }, { Delete: { TableName: 'Tokens', Key: { TokenId: 't1' } } } ] }

B. { BatchWriteItems: [ { UpdateRequest: { Key: { UserId: 'u1' }, UpdateExpression: 'SET Email = :e' } }, { DeleteRequest: { Key: { TokenId: 't1' } } } ] }

C. { TransactItems: [ { Put: { TableName: 'Users', Item: { UserId: 'u1', Email: '[e-mail]' } } }, { Delete: { TableName: 'Tokens', Key: { TokenId: 't1' } } } ] }

D. { TransactItems: [ { Update: { TableName: 'Users', Key: { UserId: 'u1' }, UpdateExpression: 'SET Email = :e' } }, { Delete: { TableName: 'Tokens', Key: { TokenId: 't1' } } } ], ReturnValuesOnConditionCheckFailure: 'ALL_OLD' }

Solution

1. Step 1: Identify correct atomic update and delete

   { TransactItems: [ { Update: { TableName: 'Users', Key: { UserId: 'u1' }, UpdateExpression: 'SET Email = :e', ExpressionAttributeValues: { ':e': '[e-mail]' } } }, { Delete: { TableName: 'Tokens', Key: { TokenId: 't1' } } } ] } uses TransactWriteItems with Update and Delete actions correctly structured.

2. Step 2: Eliminate incorrect options

   { BatchWriteItems: [ { UpdateRequest: { Key: { UserId: 'u1' }, UpdateExpression: 'SET Email = :e' } }, { DeleteRequest: { Key: { TokenId: 't1' } } } ] } uses BatchWriteItems which does not support Update; { TransactItems: [ { Put: { TableName: 'Users', Item: { UserId: 'u1', Email: '[e-mail]' } } }, { Delete: { TableName: 'Tokens', Key: { TokenId: 't1' } } } ] } uses Put which replaces entire item, not update; { TransactItems: [ { Update: { TableName: 'Users', Key: { UserId: 'u1' }, UpdateExpression: 'SET Email = :e' } }, { Delete: { TableName: 'Tokens', Key: { TokenId: 't1' } } } ], ReturnValuesOnConditionCheckFailure: 'ALL_OLD' } includes unsupported parameter ReturnValuesOnConditionCheckFailure.

3. Final Answer:

   { TransactItems: [ { Update: { TableName: 'Users', Key: { UserId: 'u1' }, UpdateExpression: 'SET Email = :e', ExpressionAttributeValues: { ':e': '[e-mail]' } } }, { Delete: { TableName: 'Tokens', Key: { TokenId: 't1' } } } ] } -> Option A

4. Quick Check:

   Use Update and Delete inside TransactItems for atomic changes [OK]

Hint: Use Update and Delete inside TransactItems for atomic writes [OK]

Common Mistakes:

• Using BatchWriteItems for updates
• Using Put instead of Update to change attributes
• Adding unsupported parameters in TransactWriteItems