GetItem (reading single item) in DynamoDB - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ query_result

intermediate

What is the output of this GetItem query?

Given a DynamoDB table Users with primary key UserID, what will be the output of this GetItem operation?

{
  TableName: "Users",
  Key: { "UserID": { "S": "123" } }
}

Assume the item with UserID "123" exists and has attributes Name: "Alice" and Age: 30.

DynamoDB

const params = {
  TableName: "Users",
  Key: { "UserID": { "S": "123" } }
};

// Assume dynamodbClient.getItem(params) returns the item

A {"Item": {"UserID": "123", "Name": "Alice", "Age": 30}}

B {"Item": {"UserID": {"S": "123"}, "Name": {"S": "Alice"}, "Age": {"N": "30"}}}

C {"Items": [{"UserID": {"S": "123"}, "Name": {"S": "Alice"}, "Age": {"N": "30"}}]}

D {"Item": null}

💡 Hint

Remember DynamoDB returns attribute values with their types.

DynamoDB GetItem returns the item attributes wrapped with their data types, such as S for string and N for number, inside the Item key.

📝 Syntax

intermediate

Which GetItem request syntax is valid?

Which of the following DynamoDB GetItem request objects is syntactically correct?

A { TableName: "Products", Key: { "ProductID": { "S": "001" } } }

B { TableName: "Products", Key: { ProductID: "001" } }

C { TableName: "Products", Key: { "ProductID": "001" } }

D { TableName: "Products", Key: { ProductID: { S: 001 } } }

💡 Hint

Check how DynamoDB expects attribute values to be typed.

DynamoDB requires attribute values in the Key to be objects with type keys like S for string and the value as a string. Option A follows this format correctly.

❓ optimization

advanced

How to optimize a GetItem request to return only specific attributes?

You want to get only the Name attribute from a DynamoDB item with UserID "789". Which GetItem request achieves this efficiently?

A { TableName: "Users", Key: { "UserID": { "S": "789" } } }

B { TableName: "Users", Key: { "UserID": { "S": "789" } }, ProjectionExpression: "UserID, Name" }

C { TableName: "Users", Key: { "UserID": { "S": "789" } }, ProjectionExpression: "Name" }

D { TableName: "Users", Key: { "UserID": { "S": "789" } }, AttributesToGet: ["Name"] }

💡 Hint

Use the recommended way to specify attributes to return in GetItem.

ProjectionExpression is the preferred and efficient way to specify which attributes to return in a GetItem request. AttributesToGet is deprecated.

🔧 Debug

advanced

Why does this GetItem request return no item?

Consider this GetItem request:

{
  TableName: "Orders",
  Key: { "OrderID": { "N": 1001 } }
}

The item with OrderID 1001 exists, but the response returns Item: null. Why?

A The number value must be passed as a string, e.g., { "N": "1001" }.

B The key attribute value should be a string, not a number.

C The table name is incorrect, causing no match.

D GetItem cannot query numeric keys.

💡 Hint

Check how DynamoDB expects number attribute values in requests.

DynamoDB requires number attribute values to be strings representing the number, not raw numbers. Passing {"N": 1001} is invalid and causes no match.

🧠 Conceptual

expert

What happens if you call GetItem with a non-existent key?

If you call DynamoDB's GetItem with a key that does not exist in the table, what will the response contain?

A The response returns an item with all attributes set to null.

B The response throws a <code>ResourceNotFoundException</code> error.

C The response returns an empty object <code>{}</code> with no <code>Item</code> key.

D The response contains <code>Item: null</code> indicating no matching item.

💡 Hint

Think about how DynamoDB signals no matching item found.

When no item matches the key, DynamoDB returns a response with Item set to null, not an error.