Transaction vs batch comparison in DynamoDB - Practice Questions

Challenge - 5 Problems

🧠 Conceptual

intermediate

Difference between DynamoDB transactions and batch operations

Which statement correctly describes a key difference between DynamoDB transactions and batch operations?

A Transactions guarantee all operations succeed or fail together, while batch operations do not provide atomicity.

B Batch operations guarantee atomicity across all items, but transactions do not.

C Transactions can only read data, while batch operations can only write data.

D Batch operations automatically retry failed requests, but transactions never retry.

💡 Hint

Think about whether all operations in the group must succeed or can partially succeed.

Transactions in DynamoDB ensure that all operations either succeed or fail as a single unit (atomicity). Batch operations can process multiple items but do not guarantee atomicity; some operations may succeed while others fail.

❓ query_result

intermediate

Result of a batch write with partial failures

You perform a BatchWriteItem request with 5 put operations. Two items exceed the provisioned throughput and fail. What is the result returned by DynamoDB?

A DynamoDB retries automatically until all 5 items succeed before returning.

B The entire batch write fails and no items are written.

C The response includes UnprocessedItems for the 2 failed items; the other 3 succeed.

D The response returns an error and no items are written.

💡 Hint

Consider how DynamoDB handles throughput limits in batch operations.

BatchWriteItem returns UnprocessedItems for requests that failed due to throughput or other transient issues. The successful writes are committed, and the client can retry the unprocessed items.

📝 Syntax

advanced

Correct syntax for a DynamoDB transaction write request

Which JSON snippet correctly represents a TransactWriteItems request with two Put operations in DynamoDB?

A { "BatchWriteItems": [ { "PutRequest": { "TableName": "Users", "Item": { "UserId": { "S": "123" }, "Name": { "S": "Alice" } } } }, { "PutRequest": { "TableName": "Orders", "Item": { "OrderId": { "S": "abc" }, "Amount": { "N": "100" } } } } ] }

B { "TransactItems": [ { "PutRequest": { "TableName": "Users", "Item": { "UserId": { "S": "123" }, "Name": { "S": "Alice" } } } }, { "PutRequest": { "TableName": "Orders", "Item": { "OrderId": { "S": "abc" }, "Amount": { "N": "100" } } } } ] }

C { "TransactWriteItems": { "Put": [ { "TableName": "Users", "Item": { "UserId": { "S": "123" }, "Name": { "S": "Alice" } } }, { "TableName": "Orders", "Item": { "OrderId": { "S": "abc" }, "Amount": { "N": "100" } } } ] } }

D { "TransactItems": [ { "Put": { "TableName": "Users", "Item": { "UserId": { "S": "123" }, "Name": { "S": "Alice" } } } }, { "Put": { "TableName": "Orders", "Item": { "OrderId": { "S": "abc" }, "Amount": { "N": "100" } } } } ] }

💡 Hint

Look for the correct key names and structure for TransactWriteItems.

TransactWriteItems expects a list under the key TransactItems, each with an operation like Put. BatchWriteItems uses BatchWriteItem and PutRequest keys. Option D matches the correct syntax for transactions.

❓ optimization

advanced

Optimizing throughput when using batch writes

You want to write 1000 items to DynamoDB efficiently. Which approach optimizes throughput and minimizes throttling?

A Split the items into batches of 25 and use BatchWriteItem with exponential backoff retries for unprocessed items.

B Send all 1000 items in a single BatchWriteItem request to minimize network calls.

C Write items one by one with PutItem requests to avoid batch size limits.

D Use TransactWriteItems for all 1000 items to ensure atomicity and speed.

💡 Hint

Consider DynamoDB limits on batch sizes and how to handle throttling.

DynamoDB BatchWriteItem limits batches to 25 items. Sending large batches causes throttling. Splitting into smaller batches and retrying unprocessed items with exponential backoff optimizes throughput.

🔧 Debug

expert

Identifying the cause of a TransactionCanceledException

A TransactWriteItems request fails with TransactionCanceledException and cancellation reasons indicating a ConditionalCheckFailed. What is the most likely cause?

A The table does not exist or is misspelled in the request.

B One or more condition expressions in the transaction failed, causing the entire transaction to abort.

C The request used BatchWriteItem syntax instead of TransactWriteItems.

D The transaction exceeded the maximum allowed size of 25 items.

💡 Hint

Think about what ConditionalCheckFailed means in a transaction context.

ConditionalCheckFailed means a condition expression evaluated to false for an item in the transaction. This causes the entire transaction to abort with TransactionCanceledException.