Why change tracking enables reactions in DynamoDB - Test Your Understanding

Practice - 5 Tasks

1fill in blank

easy

Complete the code to enable DynamoDB Streams for change tracking on a table.

DynamoDB

aws dynamodb update-table --table-name MyTable --stream-specification StreamEnabled=[1],StreamViewType=NEW_AND_OLD_IMAGES

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

Atrue

Bfalse

Cenabled

Don

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'false' disables change tracking.

Using strings like 'enabled' or 'on' are invalid here.

Setting StreamEnabled=true activates DynamoDB Streams, which tracks changes.

2fill in blank

medium

Complete the code to read change events from a DynamoDB Stream using AWS CLI.

DynamoDB

aws dynamodbstreams get-records --[1]

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

AshardIterator

BShardIterator

Cshard-iterator

DSHARDITERATOR

Attempts:

3 left

💡 Hint

Common Mistakes

Using camelCase or uppercase parameter names causes errors.

Misspelling the parameter name.

The correct parameter name is ShardIterator in PascalCase.

3fill in blank

hard

Fix the error in the code to filter DynamoDB Stream events for INSERT operations only.

DynamoDB

if event['eventName'] == '[1]': process(event)

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

AINSERT

BREMOVE

CUPDATE

DMODIFY

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'UPDATE' or 'MODIFY' instead of 'INSERT'.

Using lowercase event names.

The event name for new items added is INSERT.

4fill in blank

hard

Fill both blanks to create a DynamoDB Stream ARN for a table in region us-east-1.

DynamoDB

arn:aws:dynamodb:[1]:123456789012:table/[2]/stream/2023-01-01T00:00:00.000

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

Aus-east-1

Bus-west-2

CMyTable

DYourTable

Attempts:

3 left

💡 Hint

Common Mistakes

Mixing up region codes.

Using wrong table names in the ARN.

The region is 'us-east-1' and the table name is 'MyTable' to form the correct ARN.

5fill in blank

hard

Fill all three blanks to create a Python dictionary comprehension that maps item IDs to new values from DynamoDB Stream records where the event is INSERT.

DynamoDB

result = {record['dynamodb']['Keys']['ID']['S']: record['dynamodb']['NewImage']['Value']['S'] for record in records if record['eventName'] == '[1]' and '[2]' in record['dynamodb']['NewImage'] and record['dynamodb']['NewImage']['Value']['S'] [3] ''}

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

AINSERT

BValue

C!=

DKeys

Attempts:

3 left

💡 Hint

Common Mistakes

Using wrong event names like 'MODIFY'.

Checking wrong keys in the dictionary.

Using '=' instead of '!=' for comparison.

We filter for 'INSERT' events, check 'Value' key exists, and ensure the value is not empty using '!='.

Practice

1. What is the main purpose of change tracking in DynamoDB?

easy

A. To speed up data retrieval queries

B. To store backup copies of your data

C. To know when data changes so you can react quickly

D. To encrypt data automatically

Solution

1. Step 1: Understand change tracking concept

   Change tracking means detecting when data in the database changes.

2. Step 2: Identify why change tracking is useful

   Knowing about changes lets systems react quickly, like updating displays or sending alerts.

3. Final Answer:

   To know when data changes so you can react quickly -> Option C

4. Quick Check:

   Change tracking = React quickly [OK]

Hint: Change tracking means noticing data changes fast [OK]

Common Mistakes:

• Confusing change tracking with data backup
• Thinking it speeds up queries
• Assuming it encrypts data

2. Which DynamoDB feature is used to track changes in data?

easy

A. DynamoDB Encryption

B. DynamoDB Streams

C. DynamoDB Indexes

D. DynamoDB Backup

Solution

1. Step 1: Identify DynamoDB features related to change tracking

   DynamoDB Streams captures data changes as a stream of events.

2. Step 2: Compare other options

   Backup saves copies, Indexes speed queries, Encryption protects data but none track changes.

3. Final Answer:

   DynamoDB Streams -> Option B

4. Quick Check:

   DynamoDB Streams = Change tracking [OK]

Hint: Streams capture data changes in DynamoDB [OK]

Common Mistakes:

• Choosing Backup instead of Streams
• Confusing Indexes with change tracking
• Thinking Encryption tracks changes

3. Given a DynamoDB Stream enabled on a table, what happens when a new item is added?

medium

A. A stream record is created describing the new item

B. The table automatically backs up the new item

C. The new item is encrypted twice

D. The table index is rebuilt

Solution

1. Step 1: Understand what DynamoDB Streams do on data changes

   When an item is added, Streams create a record describing that change.

2. Step 2: Check other options

   Backup, encryption, and index rebuild are unrelated to Streams reacting to new items.

3. Final Answer:

   A stream record is created describing the new item -> Option A

4. Quick Check:

   New item added = Stream record created [OK]

Hint: Streams create records for each data change [OK]

Common Mistakes:

• Thinking backup happens automatically on add
• Confusing encryption with Streams
• Assuming index rebuild triggers on every insert

4. You set up a Lambda function to react to DynamoDB Streams but it never triggers. What is a likely cause?

medium

A. The table is encrypted

B. The Lambda function code has a syntax error

C. The table has no indexes

D. The DynamoDB Stream is not enabled on the table

Solution

1. Step 1: Check prerequisites for Lambda reacting to Streams

   Lambda triggers only if Streams are enabled on the table.

2. Step 2: Evaluate other options

   Syntax errors cause runtime failures but don't prevent triggering; indexes and encryption don't affect triggering.

3. Final Answer:

   The DynamoDB Stream is not enabled on the table -> Option D

4. Quick Check:

   Lambda triggers need Streams enabled [OK]

Hint: Enable Streams to trigger Lambda reactions [OK]

Common Mistakes:

• Blaming Lambda code syntax before checking Streams
• Thinking indexes affect Lambda triggers
• Assuming encryption blocks Lambda

5. How can change tracking with DynamoDB Streams and Lambda help maintain a real-time dashboard?

hard

A. By triggering Lambda on data changes to update the dashboard instantly

B. By backing up dashboard data every hour automatically

C. By encrypting dashboard data for security

D. By rebuilding indexes to speed up dashboard queries

Solution

1. Step 1: Understand the role of Streams and Lambda in reactions

   Streams detect data changes; Lambda reacts by running code immediately.

2. Step 2: Connect this to real-time dashboard updates

   Lambda can update the dashboard instantly when data changes, keeping it current.

3. Step 3: Eliminate unrelated options

   Backup, encryption, and index rebuild do not provide instant reaction for dashboard updates.

4. Final Answer:

   By triggering Lambda on data changes to update the dashboard instantly -> Option A

5. Quick Check:

   Streams + Lambda = Instant dashboard updates [OK]

Hint: Use Lambda triggered by Streams for instant updates [OK]

Common Mistakes:

• Confusing backup with real-time updates
• Thinking encryption updates dashboard
• Assuming index rebuild triggers updates