TransactGetItems in DynamoDB - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ query_result

intermediate

Output of a TransactGetItems with two valid keys

Given a DynamoDB table named Users with primary key UserId, what is the output of the following TransactGetItems request?

DynamoDB

TransactGetItems({
  TransactItems: [
    { Get: { TableName: "Users", Key: { UserId: { S: "user1" } } } },
    { Get: { TableName: "Users", Key: { UserId: { S: "user2" } } } }
  ]
})

A Returns only the first item found and ignores the second key.

B Returns an array with two items, each containing the full item data for user1 and user2 respectively.

C Throws a syntax error because TransactGetItems cannot have multiple items.

D Returns an empty array because TransactGetItems does not support Get operations.

💡 Hint

TransactGetItems allows multiple Get operations in one atomic request.

TransactGetItems returns all requested items atomically. Each Get operation fetches the item by key, so the output is an array with each item data.

🧠 Conceptual

intermediate

Understanding atomicity in TransactGetItems

Which statement best describes the atomicity behavior of TransactGetItems in DynamoDB?

A All requested items are retrieved atomically; either all succeed or none are returned.

B Each item is retrieved independently; some items may succeed while others fail.

C TransactGetItems only guarantees atomicity for write operations, not reads.

D Atomicity is not supported; results are returned as they are found.

💡 Hint

Think about what atomic means in database transactions.

TransactGetItems ensures that all requested items are retrieved in a single atomic operation, so either all items are returned or none if any fail.

📝 Syntax

advanced

Identify the syntax error in this TransactGetItems request

Which option contains a syntax error that will cause the TransactGetItems request to fail?

DynamoDB

TransactGetItems({
  TransactItems: [
    { Get: { TableName: "Products", Key: { ProductId: { N: "101" } } } },
    { Get: { TableName: "Products", Key: { ProductId: 102 } } }
  ]
})

A TransactItems array must contain only one Get operation.

B The first Get operation uses a string for ProductId instead of a number.

C TableName must be lowercase.

D The second Get operation's Key value for ProductId is missing the data type wrapper (N).

💡 Hint

DynamoDB requires attribute values to specify their data types explicitly.

In DynamoDB requests, attribute values must be wrapped with their data type (e.g., { N: "102" }). The second Get operation misses this, causing a syntax error.

❓ optimization

advanced

Optimizing multiple item retrieval with TransactGetItems

You need to retrieve 10 items from the same DynamoDB table by their keys. Which approach is the most efficient and atomic?

A Use a single TransactGetItems request with 10 Get operations inside TransactItems.

B Send 10 separate GetItem requests, one for each key.

C Use BatchGetItem with 10 keys in one request.

D Use Scan operation with a filter for the 10 keys.

💡 Hint

Consider atomicity and number of network calls.

TransactGetItems allows multiple Get operations in one atomic request, ensuring all items are retrieved together with a single network call.

🔧 Debug

expert

Diagnose the error from a TransactGetItems request with a missing key attribute

A TransactGetItems request fails with a ValidationException. The request is:

DynamoDB

TransactGetItems({
  TransactItems: [
    { Get: { TableName: "Orders", Key: { OrderId: { S: "123" } } } },
    { Get: { TableName: "Orders", Key: { } } }
  ]
})

A TransactGetItems cannot have more than one Get operation.

B TableName "Orders" is invalid because it contains uppercase letters.

C The second Get operation has an empty Key object, causing a ValidationException.

D The first Get operation's Key attribute type is incorrect; it should be a number.

💡 Hint

Check if all Get operations specify a valid key.

Each Get operation must specify a complete key. An empty Key object is invalid and causes a ValidationException.