Event-driven architecture patterns in DynamoDB - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to specify the event source ARN in the DynamoDB Streams trigger.

DynamoDB

event_source_arn = "[1]"

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

Aarn:aws:lambda:us-east-1:123456789012:function:ProcessOrder

Barn:aws:s3:::mybucket

Carn:aws:dynamodb:us-east-1:123456789012:table/Orders/stream/2023-01-01T00:00:00.000

Darn:aws:sqs:us-east-1:123456789012:OrderQueue

Attempts:

3 left

💡 Hint

Common Mistakes

Using an ARN from S3 or Lambda instead of DynamoDB Streams ARN.

Missing the 'stream' part in the ARN.

The event source ARN for a DynamoDB Streams trigger must point to the stream ARN of the DynamoDB table.

2fill in blank

medium

Complete the code to specify the batch size for processing DynamoDB stream records.

DynamoDB

batch_size = [1]

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

A10

B1

C100

D1000

Attempts:

3 left

💡 Hint

Common Mistakes

Setting batch size too large causing delays.

Setting batch size to 1 causing inefficient processing.

The batch size for DynamoDB Streams processing is typically set to 10 to balance throughput and latency.

3fill in blank

hard

Fix the error in the DynamoDB stream event handler code to correctly process the event records.

DynamoDB

def lambda_handler(event, context):
    for record in event['[1]']:
        print(record['eventName'])

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

Aevents

BRecords

Crecords

DEventRecords

Attempts:

3 left

💡 Hint

Common Mistakes

Using lowercase 'records' which causes a KeyError.

Using incorrect key names like 'events' or 'EventRecords'.

The DynamoDB stream event object contains a key 'Records' (capital R) which holds the list of event records.

4fill in blank

hard

Fill both blanks to create a DynamoDB stream event filter that only processes INSERT events.

DynamoDB

event_filter = {
    'eventName': ['[1]'],
    'eventSource': ['[2]']
}

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

AINSERT

BMODIFY

Cdynamodb.amazonaws.com

Daws:dynamodb

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'MODIFY' instead of 'INSERT' for eventName.

Using incorrect eventSource like 'dynamodb.amazonaws.com'.

To filter for INSERT events, use 'INSERT' for eventName and 'aws:dynamodb' for eventSource.

5fill in blank

hard

Fill all three blanks to define a DynamoDB stream event handler that logs the new image keys for INSERT events.

DynamoDB

def lambda_handler(event, context):
    for record in event['[1]']:
        if record['eventName'] == '[2]':
            new_image = record['dynamodb']['[3]']
            print(new_image)

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

ARecords

BINSERT

CNewImage

DOldImage

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'OldImage' instead of 'NewImage' for new data.

Using lowercase 'records' instead of 'Records'.

The event records are under 'Records', the event name for inserts is 'INSERT', and the new image data is under 'NewImage'.

Practice

1. What is the main purpose of using DynamoDB Streams in an event-driven architecture?

easy

A. To capture and record changes in the DynamoDB table as events

B. To store backup copies of the DynamoDB table

C. To increase the read capacity of the DynamoDB table

D. To encrypt data stored in DynamoDB

Solution

1. Step 1: Understand DynamoDB Streams role

   DynamoDB Streams capture data modification events like inserts, updates, and deletes.

2. Step 2: Identify the purpose in event-driven architecture

   These captured events trigger other processes automatically, enabling real-time reactions.

3. Final Answer:

   To capture and record changes in the DynamoDB table as events -> Option A

4. Quick Check:

   DynamoDB Streams = capture changes [OK]

Hint: Streams capture table changes as events for triggers [OK]

Common Mistakes:

• Confusing Streams with backups
• Thinking Streams increase capacity
• Assuming Streams encrypt data

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

easy

A. aws dynamodb set-stream --table MyTable --enabled true

B. aws dynamodb enable-stream --table MyTable --type NEW_IMAGE

C. aws dynamodb create-stream --table-name MyTable --view-type KEYS_ONLY

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

Solution

1. Step 1: Recall AWS CLI command for enabling streams

   The correct command uses 'update-table' with '--stream-specification' to enable streams.

2. Step 2: Verify syntax and parameters

   aws dynamodb update-table --table-name MyTable --stream-specification StreamEnabled=true,StreamViewType=NEW_AND_OLD_IMAGES correctly sets StreamEnabled=true and specifies StreamViewType as NEW_AND_OLD_IMAGES.

3. Final Answer:

   aws dynamodb update-table --table-name MyTable --stream-specification StreamEnabled=true,StreamViewType=NEW_AND_OLD_IMAGES -> Option D

4. Quick Check:

   Enable streams = update-table + stream-specification [OK]

Hint: Use update-table with stream-specification to enable streams [OK]

Common Mistakes:

• Using non-existent commands like enable-stream
• Incorrect parameter names
• Confusing create-stream with enabling streams

3. Given a DynamoDB Stream enabled with StreamViewType=NEW_IMAGE, what will an AWS Lambda function receive when an item is updated?

medium

A. Only the keys of the updated item

B. The entire item before and after the update

C. Only the new version of the item after the update

D. No data, only a notification that an update occurred

Solution

1. Step 1: Understand StreamViewType NEW_IMAGE meaning

   NEW_IMAGE sends only the new version of the item after the change.

2. Step 2: Determine what Lambda receives on update

   Lambda gets the updated item data, not the old version or just keys.

3. Final Answer:

   Only the new version of the item after the update -> Option C

4. Quick Check:

   NEW_IMAGE = new item data only [OK]

Hint: NEW_IMAGE sends only updated item data to Lambda [OK]

Common Mistakes:

• Confusing NEW_IMAGE with NEW_AND_OLD_IMAGES
• Assuming keys only are sent
• Thinking Lambda gets no data

4. You wrote a Lambda function triggered by DynamoDB Streams but it never executes. What is the most likely cause?

medium

A. The DynamoDB table does not have Streams enabled

B. The Lambda function is not subscribed to the stream

C. The Lambda function code has syntax errors

D. The DynamoDB table has no data

Solution

1. Step 1: Check if Streams are enabled

   If Streams were not enabled, no events would be generated, but question implies setup.

2. Step 2: Verify Lambda subscription to the stream

   Without subscribing Lambda to the stream, it won't trigger on events.

3. Final Answer:

   The Lambda function is not subscribed to the stream -> Option B

4. Quick Check:

   Lambda must be subscribed to stream to trigger [OK]

Hint: Ensure Lambda is subscribed to DynamoDB Stream [OK]

Common Mistakes:

• Assuming syntax errors stop invocation
• Thinking empty table stops Lambda trigger
• Ignoring subscription setup

5. You want to build a real-time notification system using DynamoDB and Lambda. Which event-driven architecture pattern best fits this use case?

hard

A. Use DynamoDB Streams to capture changes and trigger Lambda to send notifications

B. Use periodic polling of DynamoDB to check for changes and send notifications

C. Use DynamoDB Global Tables to replicate data and notify users

D. Use DynamoDB backups to trigger notifications on data changes

Solution

1. Step 1: Identify real-time event-driven pattern

   Real-time notifications require immediate reaction to data changes.

2. Step 2: Match pattern with DynamoDB Streams and Lambda

   Streams capture changes as events; Lambda processes them instantly to notify users.

3. Final Answer:

   Use DynamoDB Streams to capture changes and trigger Lambda to send notifications -> Option A

4. Quick Check:

   Streams + Lambda = real-time notifications [OK]

Hint: Streams trigger Lambda for instant notifications [OK]

Common Mistakes:

• Choosing polling which is not real-time
• Confusing replication with notifications
• Using backups which are not event triggers