TTL with Streams for archival in DynamoDB - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to enable TTL on the DynamoDB table.

DynamoDB

aws dynamodb update-time-to-live --table-name MyTable --time-to-live-specification Enabled=[1], AttributeName=expiryDate

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

ATrue

Btrue

Cenabled

Dfalse

Attempts:

3 left

💡 Hint

Common Mistakes

Using capitalized True instead of lowercase true.

Setting Enabled to false disables TTL.

TTL is enabled by setting Enabled=true in the specification.

2fill in blank

medium

Complete the code to create a DynamoDB stream for archival.

DynamoDB

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

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

AFalse

Bfalse

CTrue

Dtrue

Attempts:

3 left

💡 Hint

Common Mistakes

Using capitalized True or False.

Setting StreamEnabled to false disables the stream.

To enable streams, StreamEnabled must be set to lowercase true.

3fill in blank

hard

Fix the error in the Lambda function event handler to process DynamoDB stream records.

DynamoDB

def lambda_handler(event, context):
    for record in event['Records']:
        if record['eventName'] == '[1]':
            print('Archiving expired item')

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

AREMOVE

BDELETE

CREMOVE_ITEM

DREMOVE_RECORD

Attempts:

3 left

💡 Hint

Common Mistakes

Using DELETE instead of REMOVE.

Using non-existent event names like REMOVE_ITEM.

The event name for expired items removed by TTL is REMOVE.

4fill in blank

hard

Fill in the blank to extract the expired item and archive it.

DynamoDB

def lambda_handler(event, context):
    for record in event['Records']:
        if record['eventName'] == 'REMOVE':
            key = record['dynamodb']['[1]']
            archive_table.put_item(Item=key)

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

APartitionKey

BKeys

COldImage

DKey

Attempts:

3 left

💡 Hint

Common Mistakes

Using Keys instead of OldImage.

Using PartitionKey which is not a stream attribute.

The expired item's data is in OldImage for archiving to the archive table.

5fill in blank

hard

Fill all three blanks to filter expired items and log their IDs.

DynamoDB

def lambda_handler(event, context):
    for record in event['Records']:
        if record['eventName'] == '[1]':
            expired_item = record['dynamodb']['[2]']
            item_id = expired_item['[3]']['S']
            print(f"Expired item ID: {item_id}")

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

AREMOVE

BOldImage

Cid

DNewImage

Attempts:

3 left

💡 Hint

Common Mistakes

Using NewImage instead of OldImage.

Using wrong event name like INSERT.

Expired items trigger REMOVE events, data is in OldImage, and the ID attribute is usually named 'id'.

Practice

1. What is the main purpose of enabling TTL (Time to Live) on a DynamoDB table?

easy

A. Increase read capacity units for faster queries

B. Encrypt data at rest for security

C. Create backups of the table automatically

D. Automatically delete expired items to keep the table clean

Solution

1. Step 1: Understand TTL function

   TTL marks items with an expiration timestamp so DynamoDB can delete them automatically after expiry.

2. Step 2: Identify TTL's main benefit

   This automatic deletion helps keep the table clean without manual intervention.

3. Final Answer:

   Automatically delete expired items to keep the table clean -> Option D

4. Quick Check:

   TTL = automatic deletion [OK]

Hint: TTL deletes expired data automatically [OK]

Common Mistakes:

• Confusing TTL with encryption
• Thinking TTL creates backups
• Assuming TTL increases capacity

2. Which of the following is the correct way to enable TTL on a DynamoDB table using AWS CLI?

easy

A. aws dynamodb enable-ttl --table MyTable --attribute expiryDate

B. aws dynamodb set-ttl --table-name MyTable --ttl-attribute expiryDate

C. aws dynamodb update-time-to-live --table-name MyTable --time-to-live-specification Enabled=true,AttributeName=expiryDate

D. aws dynamodb activate-ttl --table MyTable --attributeName expiryDate

Solution

1. Step 1: Recall AWS CLI TTL command

   The correct command is 'update-time-to-live' with parameters for table name and TTL specification.

2. Step 2: Match correct syntax

   aws dynamodb update-time-to-live --table-name MyTable --time-to-live-specification Enabled=true,AttributeName=expiryDate uses the exact syntax: --time-to-live-specification Enabled=true,AttributeName=expiryDate.

3. Final Answer:

   aws dynamodb update-time-to-live --table-name MyTable --time-to-live-specification Enabled=true,AttributeName=expiryDate -> Option C

4. Quick Check:

   Correct CLI command = aws dynamodb update-time-to-live --table-name MyTable --time-to-live-specification Enabled=true,AttributeName=expiryDate [OK]

Hint: Use 'update-time-to-live' with Enabled=true [OK]

Common Mistakes:

• Using non-existent commands like enable-ttl
• Wrong parameter names
• Missing 'time-to-live-specification' flag

3. Given a DynamoDB Stream enabled on a table with TTL, what type of event will appear in the stream when an item expires and is deleted?

medium

A. INSERT

B. REMOVE

C. MODIFY

D. UPDATE

Solution

1. Step 1: Understand TTL deletion effect on streams

   When TTL deletes an item, DynamoDB Streams capture this as a REMOVE event because the item is removed.

2. Step 2: Identify correct event type

   INSERT and MODIFY happen on new or updated items, not deletions. REMOVE is the correct event for deletions.

3. Final Answer:

   REMOVE -> Option B

4. Quick Check:

   TTL deletion = REMOVE event [OK]

Hint: TTL deletions trigger REMOVE events in streams [OK]

Common Mistakes:

• Choosing INSERT or MODIFY for deletions
• Confusing UPDATE with MODIFY
• Assuming TTL triggers no stream events

4. You wrote a Lambda function triggered by DynamoDB Streams to archive deleted items. However, the Lambda never receives any events for expired items. What is the most likely cause?

medium

A. The stream is not enabled or not set to capture REMOVE events

B. TTL is not enabled on the table

C. Lambda function has no permissions to read the table

D. The table has no primary key defined

Solution

1. Step 1: Check stream configuration

   If the Lambda never receives events, the stream might be disabled or not configured to capture REMOVE events, which TTL deletions generate.

2. Step 2: Verify other causes

   TTL must be enabled, but if streams are off or missing REMOVE events, Lambda won't get notifications. Permissions or missing primary key would cause other errors.

3. Final Answer:

   The stream is not enabled or not set to capture REMOVE events -> Option A

4. Quick Check:

   Missing REMOVE events in stream = The stream is not enabled or not set to capture REMOVE events [OK]

Hint: Ensure stream captures REMOVE events for TTL deletions [OK]

Common Mistakes:

• Ignoring stream settings
• Assuming permissions cause no events
• Overlooking TTL enablement

5. You want to archive expired DynamoDB items to S3 using a Lambda triggered by Streams. Which approach ensures no data loss and handles possible Lambda failures?

hard

A. Process REMOVE events in Lambda and write directly to S3, retrying on failure

B. Use TTL to delete items, ignore streams, and periodically scan table for expired items

C. Disable TTL and manually delete items after archiving

D. Process INSERT events in Lambda and archive items before expiration

Solution

1. Step 1: Understand archival with TTL and streams

   TTL deletes expired items, streams capture REMOVE events. Lambda triggered by these events can archive data safely.

2. Step 2: Ensure reliability and no data loss

   Processing REMOVE events and writing to S3 with retries ensures data is archived even if Lambda fails temporarily.

3. Step 3: Evaluate other options

   Use TTL to delete items, ignore streams, and periodically scan table for expired items ignores streams and risks missing data. Disable TTL and manually delete items after archiving disables TTL, losing automatic cleanup. Process INSERT events in Lambda and archive items before expiration archives before expiration, which is not TTL-based archival.

4. Final Answer:

   Process REMOVE events in Lambda and write directly to S3, retrying on failure -> Option A

5. Quick Check:

   Reliable archival = Process REMOVE events in Lambda and write directly to S3, retrying on failure [OK]

Hint: Archive REMOVE events with retries for safety [OK]

Common Mistakes:

• Ignoring stream REMOVE events
• Disabling TTL unnecessarily
• Archiving on INSERT instead of REMOVE