Dead letter topics in GCP - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is a dead letter topic in Google Cloud Pub/Sub?

A dead letter topic is a special Pub/Sub topic where messages that cannot be successfully processed after multiple attempts are sent. It helps to isolate and analyze problematic messages without losing them.

beginner

Why use a dead letter topic in message processing?

Using a dead letter topic prevents message loss by capturing failed messages separately. This allows developers to investigate and fix issues without blocking the main message flow.

intermediate

How do you configure a dead letter topic in Google Cloud Pub/Sub?

You configure a dead letter topic by setting it on a subscription with a maximum delivery attempt count. After the max attempts, failed messages are sent to the dead letter topic automatically.

beginner

What happens to messages sent to a dead letter topic?

Messages sent to a dead letter topic remain there until manually reviewed or reprocessed. They are not lost and can be used to debug or retry processing later.

intermediate

Can a dead letter topic have its own subscriptions?

Yes, a dead letter topic is a normal Pub/Sub topic and can have subscriptions. This allows teams to process or analyze dead letter messages separately.

What triggers a message to be sent to a dead letter topic in Pub/Sub?

A Message is published for the first time

B Message is successfully processed

C Message fails processing after max delivery attempts

D Message is deleted manually

Messages are sent to the dead letter topic only after failing to be processed successfully after the maximum allowed delivery attempts.

Which of the following is true about dead letter topics?

A They store failed messages for later analysis

B They automatically delete messages after 1 hour

C They prevent messages from being published

D They replace the main topic

Dead letter topics store failed messages so they can be reviewed or retried later.

How do you specify the maximum delivery attempts before sending to a dead letter topic?

A Set maxDeliveryAttempts in the IAM policy

B Set maxDeliveryAttempts in the topic configuration

C Set maxDeliveryAttempts in the publisher settings

D Set maxDeliveryAttempts in the subscription configuration

The maxDeliveryAttempts is set on the subscription to control when messages move to the dead letter topic.

Can you reprocess messages from a dead letter topic?

A No, messages are deleted immediately

B Yes, by subscribing and republishing them

C No, they are archived permanently

D Yes, but only with special permissions

Messages in dead letter topics can be reprocessed by subscribing to the topic and republishing or handling them as needed.

What is the main benefit of using dead letter topics?

A Prevents message loss and aids debugging

B Improves message delivery speed

C Automatically fixes message errors

D Encrypts messages for security

Dead letter topics help prevent message loss by capturing failed messages and allow developers to debug issues.

Explain what a dead letter topic is and why it is useful in Google Cloud Pub/Sub.

Think about what happens when message processing fails repeatedly.

Describe how to configure a dead letter topic for a Pub/Sub subscription and what happens when messages reach the max delivery attempts.

Focus on subscription settings and message lifecycle.