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Question 89 of 499

Designing data processing systems →easyMultiple ChoiceObjective-mapped

Quick Answer

The answer is that the push endpoint is returning HTTP 500. This is the most likely issue because Google Cloud Pub/Sub push subscriptions require a successful acknowledgment in the form of an HTTP 200 status code; any non-200 response, especially a 500 Internal Server Error, signals to Pub/Sub that the message delivery failed, triggering automatic retries. By default, the minimum retry interval for a push subscription message retry is 10 seconds, which explains the observed behavior of messages being resent every 10 seconds without acknowledgment. On the Google Professional Data Engineer exam, this scenario tests your understanding of how HTTP status code impact directly controls delivery semantics in Pub/Sub push subscriptions—a common trap is confusing client-side errors (4xx) with server errors (5xx), as only 5xx responses trigger retries. Remember the memory tip: "200 is okay, 500 means retry the message."

PDE Designing data processing systems Practice Question

This PDE practice question tests your understanding of designing data processing systems. The scenario asks you to isolate a root cause — eliminate options that address a different problem before choosing. After answering, compare your reasoning against the explanation and wrong-answer breakdown below. Once you have made your selection, read the full explanation to reinforce the concept and understand why each distractor is designed to mislead on exam day.

Exhibit

Refer to the exhibit.
```
# Pub/Sub subscription config
projects/my-project/subscriptions/my-sub:
  topic: projects/my-project/topics/my-topic
  ackDeadlineSeconds: 10
  pushConfig:
    pushEndpoint: https://my-endpoint.example.com/push
    oidcToken:
      serviceAccountEmail: sa@my-project.iam.gserviceaccount.com
```

A team has set up a push subscription to an HTTPS endpoint. They notice that messages are not being acknowledged and are resent every 10 seconds. What is the most likely issue?

Clue words in this question

Noticing these words before you look at the options changes how you read each choice.

Clue: "most likely"
Why it matters: Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.

Question 1easymultiple choice

Full question →

Exhibit

Refer to the exhibit.
```
# Pub/Sub subscription config
projects/my-project/subscriptions/my-sub:
  topic: projects/my-project/topics/my-topic
  ackDeadlineSeconds: 10
  pushConfig:
    pushEndpoint: https://my-endpoint.example.com/push
    oidcToken:
      serviceAccountEmail: sa@my-project.iam.gserviceaccount.com
```

A
The push endpoint is returning HTTP 200 but taking too long to process
Why wrong: If the endpoint eventually returns 200, Pub/Sub will acknowledge the message after the response.
B
The push endpoint is returning HTTP 500
Any non-200 response (e.g., 500) causes Pub/Sub to retry; 500 indicates a server error.
C
The push endpoint is returning HTTP 200 with 'ack' in the body
Why wrong: Pub/Sub only considers HTTP status code; body content does not affect acknowledgment.
D
The push endpoint is returning HTTP 400
Why wrong: A 400 error also causes retries, but 500 is more indicative of a failure; however, both cause retries, but B is a common issue.

Full breakdown with real-world context →

Answer choices

Why each option matters

Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.

Correct answer & explanation

✓

The push endpoint is returning HTTP 500

In Google Cloud Pub/Sub push subscriptions, the subscriber must acknowledge messages by returning an HTTP 200 status code. If the endpoint returns HTTP 500, Pub/Sub interprets this as a failure and will retry delivery with exponential backoff, but the default minimum retry interval is 10 seconds. This matches the observed behavior of messages being resent every 10 seconds without acknowledgment.

Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.

Answer analysis

Option-by-option breakdown

For each option: why learners choose it and why it is or isn't the right answer here.

✗
The push endpoint is returning HTTP 200 but taking too long to process
Why it's wrong here
If the endpoint eventually returns 200, Pub/Sub will acknowledge the message after the response.
✓
The push endpoint is returning HTTP 500
Why this is correct
Any non-200 response (e.g., 500) causes Pub/Sub to retry; 500 indicates a server error.
Clue confirmation
The clue word "most likely" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
✗
The push endpoint is returning HTTP 200 with 'ack' in the body
Why it's wrong here
Pub/Sub only considers HTTP status code; body content does not affect acknowledgment.
✗
The push endpoint is returning HTTP 400
Why it's wrong here
A 400 error also causes retries, but 500 is more indicative of a failure; however, both cause retries, but B is a common issue.

Common exam traps

Common exam trap: answer the scenario, not the keyword

Google Cloud often tests the misconception that the response body or processing time affects acknowledgment, when in fact only the HTTP status code determines whether a message is acknowledged or retried.

Detailed technical explanation

How to think about this question

Pub/Sub push subscriptions rely on the HTTP response status code for acknowledgment: 200–299 is success, 300–499 is a client error (no retry for 400–499 except 408 and 429 which trigger retry), and 500–599 triggers retry with exponential backoff starting at 10 seconds. The 10-second interval is the minimum retry delay for server errors, and if the endpoint continues to return 500, the retry interval will increase over time up to a maximum of 600 seconds.

KKey Concepts to Remember

Read the scenario before looking for a memorised answer.
Find the constraint that changes the correct option.
Eliminate answers that are true in general but not in this case.

TExam Day Tips

Watch for words such as best, first, most likely and least administrative effort.
Review why wrong options are wrong, not only why the correct option is correct.

Key takeaway

Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.

Real-world example

How this comes up in practice

A cloud solutions architect for a retail company is evaluating services for a new workload. The correct answer here reflects best practice for the specific scenario described — not a general cloud recommendation. Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option. Cloud exam questions reward reading the constraint carefully: the same technology can be right or wrong depending on the use case.

What to study next

Got this wrong? Here's your next step.

Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.

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FAQ

Questions learners often ask

What does this PDE question test?

Designing data processing systems — This question tests Designing data processing systems — Read the scenario before looking for a memorised answer..

What is the correct answer to this question?

The correct answer is: The push endpoint is returning HTTP 500 — In Google Cloud Pub/Sub push subscriptions, the subscriber must acknowledge messages by returning an HTTP 200 status code. If the endpoint returns HTTP 500, Pub/Sub interprets this as a failure and will retry delivery with exponential backoff, but the default minimum retry interval is 10 seconds. This matches the observed behavior of messages being resent every 10 seconds without acknowledgment.

What should I do if I get this PDE question wrong?

Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.

Are there clue words in this question I should notice?

Yes — watch for: "most likely". Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.

What is the key concept behind this question?

Read the scenario before looking for a memorised answer.

About these practice questions

Courseiva creates original exam-style practice questions with explanations and wrong-answer analysis. It does not publish real exam questions, exam dumps, or protected exam content. Learn why practice questions differ from exam dumps →

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Same concept, more angles

1 more ways this is tested on PDE

These questions test the same concept from different angles. Work through them to make sure you can recognise it however the exam phrases it.

Variation 1. Drag and drop the steps to set up a Pub/Sub topic with a push subscription to an HTTPS endpoint into the correct order.

medium

Why : Push subscriptions send messages to a configured HTTPS endpoint.

Last reviewed: Jun 30, 2026

Question Discussion

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