The answer is that the container is listening on port 3000 instead of port 8080. This is the most likely cause of a Cloud Run deployment failure because Cloud Run requires your container to listen on the port defined by the `PORT` environment variable, which defaults to 8080. When your application is hardcoded to port 3000, the Cloud Run runtime cannot reach it for health checks or route incoming requests, causing the deployment to fail with a port mismatch error. On the Google Professional Cloud Architect exam, this scenario tests your understanding of Cloud Run’s container runtime contract and the importance of respecting environment variables over hardcoded values. A common trap is assuming any port will work, but Cloud Run explicitly injects `PORT=8080` and expects the container to honor it. Remember the memory tip: “8080 is the only port that matters in Cloud Run”—if your app listens elsewhere, the deployment will fail.
Google PCA Practice Question: Analyze and optimize technical and business processes
This PCA practice question tests your understanding of analyze and optimize technical and business processes. 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.
```
ERROR: (gcloud.beta.run.deploy) The user-provided container failed to start and listen on the port defined provided by the PORT=8080 environment variable.
Logs:
2023-05-01 12:00:00.000 INFO server started on port 3000
```
A developer is deploying a containerized application to Cloud Run. The deployment fails with the error above. 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.
Refer to the exhibit.
```
ERROR: (gcloud.beta.run.deploy) The user-provided container failed to start and listen on the port defined provided by the PORT=8080 environment variable.
Logs:
2023-05-01 12:00:00.000 INFO server started on port 3000
```
A
The container is listening on port 3000 instead of 8080.
Cloud Run requires the container to listen on the port defined by the PORT environment variable, which defaults to 8080.
B
The container health check is misconfigured.
Why wrong: The error is about port availability, not health checks.
C
The container startup script fails.
Why wrong: The logs indicate successful startup.
D
The container does not have a web server.
Why wrong: The logs show it started on port 3000, so a server is running.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
The container is listening on port 3000 instead of 8080.
Cloud Run requires containers to listen on the port defined by the `PORT` environment variable, which defaults to 8080. If the container is hardcoded to listen on port 3000, Cloud Run's health checks and routing will fail because the runtime cannot reach the application on the expected port, causing the deployment to fail.
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 container is listening on port 3000 instead of 8080.
Why this is correct
Cloud Run requires the container to listen on the port defined by the PORT environment variable, which defaults to 8080.
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 container health check is misconfigured.
Why it's wrong here
The error is about port availability, not health checks.
✗
The container startup script fails.
Why it's wrong here
The logs indicate successful startup.
✗
The container does not have a web server.
Why it's wrong here
The logs show it started on port 3000, so a server is running.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Google Cloud often tests the misconception that any port mismatch will cause a health check failure, but the actual trap is that Cloud Run's deployment validation checks port binding before the container is considered healthy, so a wrong port causes an immediate deployment failure, not a post-deployment health check issue.
Trap categories for this question
Command / output trap
The logs show it started on port 3000, so a server is running.
Detailed technical explanation
How to think about this question
Cloud Run injects the `PORT` environment variable (default 8080) into the container at runtime, and the container must bind to that port. Under the hood, Cloud Run uses a reverse proxy (gVisor-based) that forwards requests to the container's port; if the container listens on a different port, the proxy cannot route traffic, resulting in a deployment error. In real-world scenarios, developers often hardcode ports in frameworks like Express.js (`app.listen(3000)`) or Flask (`app.run(port=3000)`), forgetting to read the `PORT` environment variable.
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.
Related glossary terms
Concepts from this question explained
These glossary pages explain the core terms tested in this PCA question in full detail.
Analyze and optimize technical and business processes — This question tests Analyze and optimize technical and business processes — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: The container is listening on port 3000 instead of 8080. — Cloud Run requires containers to listen on the port defined by the `PORT` environment variable, which defaults to 8080. If the container is hardcoded to listen on port 3000, Cloud Run's health checks and routing will fail because the runtime cannot reach the application on the expected port, causing the deployment to fail.
What should I do if I get this PCA 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.
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