SNS topics and subscriptions in AWS - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ service_behavior

intermediate

SNS Topic Message Delivery Behavior

You have an SNS topic with multiple email subscriptions. If a message is published to the topic, what happens to the message delivery?

A The message is stored in the topic and must be pulled by each subscriber.

B The message is sent to only one randomly selected email subscription.

C The message is sent to the first subscription created and ignored for others.

D The message is sent to all subscribed email endpoints simultaneously.

💡 Hint

Think about how SNS fan-out messaging works.

SNS topics deliver messages to all subscribed endpoints simultaneously. It is a push-based system that fans out messages to every subscription.

❓ Configuration

intermediate

SNS Subscription Protocols

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

A ftp

B sms

C email

D https

💡 Hint

Consider common protocols supported by SNS for message delivery.

SNS supports email, SMS, HTTP, HTTPS, SQS, Lambda, and application protocols. FTP is not supported.

❓ security

advanced

Restricting SNS Topic Access

You want to restrict who can publish messages to your SNS topic. Which AWS feature should you use to enforce this?

A SNS Subscription Filter Policy

B VPC Security Group attached to the SNS topic

C SNS Topic Policy with specific IAM conditions

D AWS WAF attached to the SNS topic

💡 Hint

Think about how AWS controls permissions on SNS topics.

SNS Topic Policies allow you to specify who can publish or subscribe to the topic using IAM conditions. Security groups and WAF do not apply to SNS topics.

❓ Architecture

advanced

Designing Reliable SNS to SQS Integration

You have an SNS topic that sends messages to multiple SQS queues. How can you ensure that no messages are lost if one SQS queue is temporarily unavailable?

A Enable dead-letter queues (DLQ) on the SQS queues to capture undelivered messages.

B Configure SNS to retry sending messages indefinitely until the SQS queue is available.

C Use SNS FIFO topics to guarantee message delivery to all SQS queues.

D Set the SQS queue visibility timeout to zero.

💡 Hint

Consider how to handle message failures in SQS subscriptions.

Dead-letter queues capture messages that can't be delivered or processed, preventing message loss. SNS retries have limits and FIFO topics do not guarantee no loss if queues are down.

✅ Best Practice

expert

Optimizing SNS Topic for High Throughput

You expect a very high volume of messages published to an SNS topic. Which approach best optimizes throughput and scalability?

A Publish messages synchronously to SNS to ensure delivery speed.

B Use multiple SNS topics partitioned by message type and aggregate downstream.

C Use SNS FIFO topics to maintain order and increase throughput.

D Use a single SNS topic with a large number of subscriptions to distribute load.

💡 Hint

Think about how to scale SNS topics horizontally.

Partitioning messages across multiple SNS topics reduces bottlenecks and improves throughput. FIFO topics limit throughput and synchronous publishing slows performance.