DynamoDB Streams concept - Practice Problems & Coding Challenges

Challenge - 5 Problems

🧠 Conceptual

intermediate

What does DynamoDB Streams capture?

DynamoDB Streams records changes in a DynamoDB table. What kind of changes does it capture?

A All item-level modifications including inserts, updates, and deletes

B Only deleted items from the table

C Only new items added to the table

D Only changes to table indexes

💡 Hint

Think about what you want to track if you want a full history of changes.

DynamoDB Streams captures all item-level changes: inserts, updates, and deletes, allowing applications to react to any modification.

❓ query_result

intermediate

What is the output of this DynamoDB Stream record?

Given a DynamoDB Stream record for an update event, what does the 'NewImage' attribute contain?

DynamoDB

StreamRecord: {
  "eventName": "MODIFY",
  "dynamodb": {
    "NewImage": {"Id": {"S": "101"}, "Status": {"S": "Shipped"}},
    "OldImage": {"Id": {"S": "101"}, "Status": {"S": "Pending"}}
  }
}

A The item data after the update

B The item data before the update

C Only the changed attributes

D The entire table data

💡 Hint

NewImage means the new state of the item after the change.

The 'NewImage' attribute contains the full item data after the update event.

📝 Syntax

advanced

Which option correctly enables DynamoDB Streams on a table with NEW_AND_OLD_IMAGES?

You want to enable DynamoDB Streams on a table to capture both new and old images of items. Which AWS CLI command is correct?

DynamoDB

aws dynamodb update-table --table-name Orders --stream-specification StreamEnabled=true,StreamViewType=NEW_AND_OLD_IMAGES

A aws dynamodb update-table --table-name Orders --stream-specification StreamEnabled=true;StreamViewType=NEW_AND_OLD_IMAGES

B aws dynamodb update-table --table-name Orders --stream-specification StreamEnabled=true StreamViewType=NEW_AND_OLD_IMAGES

C aws dynamodb update-table --table-name Orders --stream-specification StreamEnabled: true, StreamViewType: NEW_AND_OLD_IMAGES

D aws dynamodb update-table --table-name Orders --stream-specification StreamEnabled=true,StreamViewType=NEW_AND_OLD_IMAGES

💡 Hint

Check the correct syntax for comma-separated key-value pairs in AWS CLI.

The correct syntax uses comma-separated key-value pairs without spaces or colons.

❓ optimization

advanced

How to minimize costs when using DynamoDB Streams?

You want to reduce costs while using DynamoDB Streams for a high-traffic table. Which approach helps minimize costs?

A Disable Streams and poll the table directly for changes

B Enable Streams with NEW_AND_OLD_IMAGES to capture full item data

C Enable Streams with KEYS_ONLY view type to reduce data volume

D Use Streams with NEW_IMAGE and process all attributes

💡 Hint

Less data in streams means less processing and storage cost.

Using KEYS_ONLY reduces the amount of data captured in streams, lowering costs.

🔧 Debug

expert

Why does this Lambda function triggered by DynamoDB Streams fail with a TypeError?

A Lambda function processes DynamoDB Stream events. It tries to access event.Records[0].dynamodb.NewImage.Name.S but fails with TypeError: Cannot read property 'S' of undefined. What is the likely cause?

DynamoDB

exports.handler = async (event) => {
  const name = event.Records[0].dynamodb.NewImage.Name.S;
  console.log(name);
};

A The event.Records array is empty

B The 'Name' attribute does not exist in NewImage for this event

C The Lambda function lacks permissions to read the stream

D The stream is disabled on the DynamoDB table

💡 Hint

Check if the attribute you access is always present in the stream record.

If the 'Name' attribute is missing in NewImage, accessing .S causes a TypeError.