This PCSE practice question tests your understanding of cloud run port environment variable. The scenario asks you to isolate a root cause — eliminate options that address a different problem before choosing. A key principle to apply: cloud Run PORT environment variable. 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
Error: Container failed to start. Failed to start and then listen on the port defined by the PORT environment variable.
Refer to the exhibit. A Cloud Run service fails to start and shows the above error. What is the most likely cause?
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.
Exhibit
Error: Container failed to start. Failed to start and then listen on the port defined by the PORT environment variable.
A
The container requires more memory than allocated
Why wrong: Memory issues typically cause OOM errors or slow performance, not a failure to listen on a port.
B
The PORT environment variable is not defined in the container
Why wrong: If PORT were missing, the error would likely indicate that; the error says the container failed to listen on the port defined by PORT, implying PORT is set but the container isn't listening.
C
The application is configured to listen on a different port than the one specified by PORT
Cloud Run injects PORT; the container must bind to that port. If the app listens on another port, it fails to start.
D
The number of concurrent requests exceeds the container's limit
Why wrong: Concurrent request limits cause throttling after startup, not startup failures.
The answer is that the application is configured to listen on a different port than the one specified by the PORT environment variable. This is correct because Cloud Run injects the PORT environment variable (defaulting to 8080) and expects the container to bind to that exact port; a startup error explicitly stating the container is not listening on the defined port confirms a mismatch between the application’s configured port and the value Cloud Run expects. On the Google Professional Cloud Security Engineer exam, this tests your understanding of container runtime contract fundamentals—a common trap is assuming the error relates to a missing PORT variable or resource limits, but the error message itself pinpoints a listening port conflict. A key memory tip: think of PORT as a strict handshake—your app must shake the exact hand Cloud Run offers, or the service fails to start.
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 application is configured to listen on a different port than the one specified by PORT
Option C is correct because the error explicitly states the container is not listening on the port defined by PORT. Cloud Run expects the container to bind to the port specified in the PORT env var (default 8080). Option A is wrong; insufficient memory causes different errors. Option B is wrong; the error is about listening, not the variable missing. Option D is wrong; concurrent requests are runtime limits, not startup issues.
Key principle: Cloud Run PORT environment variable
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 container requires more memory than allocated
Why it's wrong here
Memory issues typically cause OOM errors or slow performance, not a failure to listen on a port.
✗
The PORT environment variable is not defined in the container
Why it's wrong here
If PORT were missing, the error would likely indicate that; the error says the container failed to listen on the port defined by PORT, implying PORT is set but the container isn't listening.
✓
The application is configured to listen on a different port than the one specified by PORT
Why this is correct
Cloud Run injects PORT; the container must bind to that port. If the app listens on another port, it fails to start.
Clue confirmation
The clue word "most likely" in the question point toward this answer.
Related concept
Cloud Run PORT environment variable
✗
The number of concurrent requests exceeds the container's limit
Why it's wrong here
Concurrent request limits cause throttling after startup, not startup failures.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Many certification questions include familiar terms but test a specific constraint. Read the exact wording before choosing an answer that is generally true but wrong for this case.
Detailed technical explanation
How to think about this question
Treat this as a scenario question. Identify the problem, the constraint, and the best action. Then compare each option against those facts.
KKey Concepts to Remember
Cloud Run PORT environment variable
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
Cloud Run PORT environment variable
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. Cloud Run PORT environment variable 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.
Review cloud Run PORT environment variable, then practise related PCSE questions on the same topic to reinforce the concept.
The correct answer is: The application is configured to listen on a different port than the one specified by PORT — Option C is correct because the error explicitly states the container is not listening on the port defined by PORT. Cloud Run expects the container to bind to the port specified in the PORT env var (default 8080). Option A is wrong; insufficient memory causes different errors. Option B is wrong; the error is about listening, not the variable missing. Option D is wrong; concurrent requests are runtime limits, not startup issues.
What should I do if I get this PCSE question wrong?
Review cloud Run PORT environment variable, then practise related PCSE questions on the same topic to reinforce the concept.
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?
Cloud Run PORT environment variable
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