The answer is that the new environment variable causes the application to fail its startup or health check. This is correct because Cloud Run performs health checks on every new revision before routing traffic to it; if the application reads the environment variable at startup and crashes—due to an invalid value, missing dependency, or misconfiguration—the health check fails, and the deployment is rejected. On the Google Professional Cloud Developer exam, this scenario tests your understanding of how Cloud Run’s revision lifecycle interacts with environment configuration, often appearing as a trap where candidates blame the deployment pipeline or authentication settings instead of the application’s runtime behavior. A common memory tip is “Env vars are code, too”—treat every environment variable as a potential breaking change that must be validated, just like a code commit.
PCD Deploying applications Practice Question
This PCD practice question tests your understanding of deploying applications. 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.
Your company is deploying a web application on Cloud Run using a continuous deployment pipeline from Cloud Build. The application is built as a Docker container and pushed to Container Registry. The Cloud Run service is configured with the '--no-allow-unauthenticated' flag. You have set up Cloud Build triggers to build and deploy on commits to the main branch. The deployment works correctly for the first few commits, but after adding a new environment variable in the Cloud Build configuration file (cloudbuild.yaml), the deployment fails with an error that the Cloud Run service cannot be updated because the new revision fails health checks. The application code has not changed. 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: "first"
Why it matters: Order matters here. You are being tested on which action comes before the others — not which action is generally useful.
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.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
The new environment variable causes the application to fail its startup or health check.
Option D is correct because the application code has not changed, yet the deployment fails health checks immediately after adding a new environment variable. This indicates that the application is likely reading that variable at startup and crashing or failing its readiness probe due to an invalid value, missing dependency, or misconfiguration. Cloud Run requires the new revision to pass health checks (e.g., HTTP GET on the configured port) before it can serve traffic; if the variable causes the app to exit or hang, the revision is considered unhealthy and the update is rejected.
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 Cloud Build service account does not have permission to update the Cloud Run service.
Why it's wrong here
The deployment worked before, so permissions are likely correct.
✗
The new environment variable exceeds the maximum size limit for environment variables in Cloud Run.
Why it's wrong here
Cloud Run has limits but a single variable is unlikely to exceed them.
✗
The health check configuration in the Cloud Run service was overwritten by the new deployment.
Why it's wrong here
Health check config is not typically overwritten unless specified.
✓
The new environment variable causes the application to fail its startup or health check.
Why this is correct
A misconfigured environment variable can cause the app to crash.
Clue confirmation
The clue words "first", "most likely" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Cisco often tests the misconception that environment variables are harmless metadata and cannot cause deployment failures, when in fact they can break application startup logic or health check responses.
Detailed technical explanation
How to think about this question
Cloud Run uses HTTP-based health checks (startup and liveness probes) that must return a 200–399 status code within a timeout period (default 1 second for liveness, 4 seconds for startup). If the application fails to bind to the configured port or returns a non-2xx/3xx response, the revision is marked unhealthy and the deployment is rolled back. Environment variables are injected into the container at runtime and can cause immediate failure if the app expects a specific format, a file path, or a secret that doesn't exist.
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 company's IT admin needs to give a contractor read-only access to production logs without sharing account credentials. Using role-based access control (RBAC) and temporary scoped permissions — not a permanent shared password — is the correct pattern. Questions like this test whether you can apply least-privilege access across cloud identity services.
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.
Deploying applications — This question tests Deploying applications — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: The new environment variable causes the application to fail its startup or health check. — Option D is correct because the application code has not changed, yet the deployment fails health checks immediately after adding a new environment variable. This indicates that the application is likely reading that variable at startup and crashing or failing its readiness probe due to an invalid value, missing dependency, or misconfiguration. Cloud Run requires the new revision to pass health checks (e.g., HTTP GET on the configured port) before it can serve traffic; if the variable causes the app to exit or hang, the revision is considered unhealthy and the update is rejected.
What should I do if I get this PCD 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: "first", "most likely". Order matters here. You are being tested on which action comes before the others — not which action is generally useful.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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