SNS notification types (email, SMS, Lambda) in AWS - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ service_behavior

intermediate

SNS Email Subscription Behavior

When an AWS SNS topic has an email subscription, what happens immediately after a message is published to the topic?

A The message is sent directly to the email address without any confirmation.

B The email address receives a confirmation request and must confirm before receiving messages.

C The message is stored in an S3 bucket linked to the email subscription.

D The email subscription triggers a Lambda function to send the message.

💡 Hint

Think about how SNS ensures the email owner wants to receive messages.

SNS requires email subscriptions to be confirmed by the recipient before messages are delivered. This prevents unwanted emails.

❓ service_behavior

intermediate

SNS SMS Message Delivery Limits

What is a key limitation when sending SMS messages via AWS SNS?

A SNS can send SMS messages only within the same AWS region as the topic.

B SNS requires a Lambda function to process SMS messages before sending.

C SNS SMS messages have a maximum size of 140 bytes and may be split if longer.

D SNS SMS messages can only be sent to phone numbers verified in the AWS account.

💡 Hint

Consider SMS message size limits in telecom.

SMS messages have size limits (usually 140 bytes). SNS splits longer messages into multiple SMS segments automatically.

❓ Architecture

advanced

SNS with Lambda Subscription Behavior

Which statement correctly describes what happens when an SNS topic has a Lambda function subscribed and a message is published?

A SNS invokes the Lambda function asynchronously immediately after publishing the message.

B SNS invokes the Lambda function synchronously and waits for the function to complete before returning.

C SNS stores the message in S3 and triggers Lambda asynchronously after a delay.

D SNS requires the Lambda function to poll the topic to receive messages.

💡 Hint

Think about how SNS triggers Lambda functions.

SNS invokes Lambda functions asynchronously immediately after a message is published to the topic.

❓ security

advanced

Securing SNS Email Subscriptions

Which method best protects an SNS email subscription from unauthorized subscription requests?

A Configure SNS to send messages only to verified email addresses in AWS SES.

B Enable server-side encryption on the SNS topic.

C Restrict SNS topic access using IAM policies only.

D Use subscription confirmation emails that require user action to activate.

💡 Hint

Think about how SNS confirms email ownership.

Subscription confirmation emails require the recipient to confirm the subscription, preventing unauthorized subscriptions.

✅ Best Practice

expert

Designing Reliable SNS Notifications with Multiple Protocols

You want to ensure that a critical alert message sent via SNS reaches both an email recipient and triggers a Lambda function. Which design approach ensures the highest reliability and fault tolerance?

A Create one SNS topic with both email and Lambda subscriptions; rely on SNS retry policies for failures.

B Create separate SNS topics for email and Lambda; publish the message twice from your application.

C Use one SNS topic with email subscription only; Lambda polls the email inbox for messages.

D Send the email and invoke the Lambda function directly from your application, bypassing SNS.

💡 Hint

Consider SNS built-in retry and fan-out capabilities.

Using one SNS topic with multiple subscriptions leverages SNS's fan-out and retry mechanisms, improving reliability and simplifying architecture.

Practice

1. Which of the following is NOT a valid protocol for an AWS SNS subscription?

easy

A. email

B. sms

C. lambda

D. ftp

Solution

1. Step 1: Review SNS supported protocols

   AWS SNS supports protocols like email, sms, and lambda for subscriptions.

2. Step 2: Identify unsupported protocol

   FTP is not supported as a protocol for SNS subscriptions.

3. Final Answer:

   ftp -> Option D

4. Quick Check:

   Supported protocols exclude ftp [OK]

Hint: Remember SNS supports email, sms, lambda but not ftp [OK]

Common Mistakes:

• Confusing FTP as supported protocol
• Thinking HTTP is the only protocol
• Mixing SNS with S3 protocols

2. Which is the correct way to specify an SMS subscription protocol in AWS SNS?

easy

A. Protocol: 'sms', Endpoint: '[e-mail]'

B. Protocol: 'email', Endpoint: '[phone]'

C. Protocol: 'sms', Endpoint: '[phone]'

D. Protocol: 'lambda', Endpoint: '[phone]'

Solution

1. Step 1: Understand protocol and endpoint types

   For SMS, protocol must be 'sms' and endpoint is a phone number with country code.

2. Step 2: Match correct protocol and endpoint

   Protocol: 'sms', Endpoint: '[phone]' correctly uses 'sms' protocol and a phone number endpoint.

3. Final Answer:

   Protocol: 'sms', Endpoint: '[phone]' -> Option C

4. Quick Check:

   SMS needs phone number endpoint [OK]

Hint: SMS protocol requires phone number endpoint format [OK]

Common Mistakes:

• Using email as protocol for SMS
• Using email address as SMS endpoint
• Using lambda protocol with phone number

3. Given this AWS SNS subscription code snippet:

sns.subscribe({
  Protocol: 'lambda',
  Endpoint: 'arn:aws:lambda:us-east-1:123456789012:function:ProcessMessage'
});

What happens when a message is published to this SNS topic?

medium

A. The Lambda function 'ProcessMessage' is invoked with the message payload.

B. The message is sent as an SMS to the Lambda function ARN.

C. The message is sent as an email to the Lambda function.

D. The subscription will fail because Lambda cannot be an endpoint.

Solution

1. Step 1: Identify protocol and endpoint meaning

   Protocol 'lambda' means SNS invokes the specified Lambda function ARN when a message is published.

2. Step 2: Understand message delivery behavior

   The Lambda function 'ProcessMessage' is called with the message payload as input.

3. Final Answer:

   The Lambda function 'ProcessMessage' is invoked with the message payload. -> Option A

4. Quick Check:

   Lambda protocol triggers function invocation [OK]

Hint: Lambda protocol triggers function call, not email or SMS [OK]

Common Mistakes:

• Thinking Lambda receives email or SMS
• Assuming subscription fails
• Confusing endpoint ARN with phone/email

4. You created an SNS subscription with protocol 'email' but the subscriber never receives messages. What is the most likely cause?

medium

A. The email address was not confirmed by the subscriber.

B. The SNS topic does not support email protocol.

C. The subscription endpoint was set to a phone number.

D. Lambda function is not attached to the subscription.

Solution

1. Step 1: Understand email subscription confirmation

   Email subscriptions require the recipient to confirm by clicking a link in a confirmation email.

2. Step 2: Identify common cause of no delivery

   If the email is not confirmed, SNS will not send notifications to that address.

3. Final Answer:

   The email address was not confirmed by the subscriber. -> Option A

4. Quick Check:

   Email subscriptions need confirmation [OK]

Hint: Email subscriptions require confirmation before delivery [OK]

Common Mistakes:

• Assuming SNS does not support email
• Confusing phone number as email endpoint
• Expecting Lambda involvement in email subscription

5. You want to send an SMS notification and also trigger a Lambda function whenever a message is published to an SNS topic. How should you configure the subscriptions?

hard

A. Create one subscription with protocol 'email' and endpoint as phone number, and another with protocol 'lambda' and endpoint as Lambda ARN.

B. Create one subscription with protocol 'sms' and endpoint as phone number, and another with protocol 'lambda' and endpoint as Lambda ARN.

C. Create one subscription with protocol 'lambda' and endpoint as phone number, and another with protocol 'sms' and endpoint as Lambda ARN.

D. Create one subscription with protocol 'sms' and endpoint as Lambda ARN, and another with protocol 'lambda' and endpoint as phone number.

Solution

1. Step 1: Understand protocol and endpoint matching

   SMS protocol requires a phone number endpoint; Lambda protocol requires Lambda function ARN.

2. Step 2: Configure two subscriptions correctly

   Create one subscription with protocol 'sms' and phone number endpoint, and another with protocol 'lambda' and Lambda ARN endpoint.

3. Final Answer:

   Create one subscription with protocol 'sms' and endpoint as phone number, and another with protocol 'lambda' and endpoint as Lambda ARN. -> Option B

4. Quick Check:

   Match protocol to correct endpoint type [OK]

Hint: Match SMS to phone number, Lambda to function ARN [OK]

Common Mistakes:

• Mixing endpoints and protocols
• Using email protocol for SMS
• Assigning Lambda ARN as SMS endpoint