The answer is that the frontend pods are not using the correct DNS name that includes the namespace. In Kubernetes, cross-namespace service discovery requires a fully qualified domain name (FQDN) like `backend-svc.backend-ns.svc.cluster.local`; simply using `backend-svc` resolves only within the same namespace, causing a connection refused error because the DNS query fails to locate the service. This scenario tests your understanding of Kubernetes DNS resolution and service discovery, a common topic on the Google Professional Cloud Developer exam where cluster upgrades can reset DNS configurations or expose namespace-scoped naming assumptions. A frequent trap is assuming that service names work globally across namespaces, but Kubernetes defaults to namespace-scoped DNS unless an FQDN or a ServiceImport (in multi-cluster setups) is used. Remember the mnemonic: “Same space, short name; cross space, full name.”
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 runs a multi-tier application on GKE. The frontend is a Deployment with 5 replicas, backend is a StatefulSet with 3 replicas, and a database runs on Cloud SQL. Recently, after a cluster upgrade, the frontend pods are failing with 'Connection refused' errors when trying to reach the backend service. The backend pods are running and healthy. You have verified that the Service and Endpoints objects exist. The backend service is of type ClusterIP on port 8080, and the frontend uses the service name 'backend-svc'. The frontend pods are in a different namespace 'frontend-ns', while the backend is in 'backend-ns'. What is the most likely cause of the error?
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.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
The frontend pods are not using the correct DNS name that includes the namespace.
Option C is correct because the frontend is in a different namespace and not using the fully qualified DNS name (backend-svc.backend-ns.svc.cluster.local) or the namespace is not properly configured for DNS resolution. Option A is wrong because the service type ClusterIP does not require a firewall rule. Option B is wrong because the StatefulSet is backed by a Service that provides DNS. Option D is wrong because network policy would cause timeout not connection refused.
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 backend Service is not exposed via an Ingress, so it is not reachable from other namespaces.
Why it's wrong here
ClusterIP services are reachable across namespaces via DNS.
✗
The StatefulSet pods are not part of the backend Service's selector.
Why it's wrong here
If endpoints exist, selector is correct.
✗
A NetworkPolicy is blocking traffic between the namespaces.
Why it's wrong here
NetworkPolicy would cause timeout, not connection refused.
✓
The frontend pods are not using the correct DNS name that includes the namespace.
Why this is correct
Cross-namespace access requires the full DNS name.
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.
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
This question should be treated as a scenario, not a definition check. Identify the problem, the constraint and the best action. Then compare each option against those facts.
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.
Use explanations to understand the rule behind the answer.
TExam Day Tips
→Underline the problem statement mentally.
→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 media company stores terabytes of video archives that are accessed once a year for audit purposes. Moving these objects to a cold storage tier (Azure Archive, S3 Glacier, or Google Nearline) costs a fraction of hot storage. Questions like this test whether you understand storage tiers, access frequency tradeoffs, and retrieval latency requirements.
What to study next
Got this wrong? Here's your next step.
Identify which PCD exam domain this question belongs to, then review the specific concept being tested. Practise related questions in that domain and focus on understanding why each wrong answer is tempting — not just why the correct answer is right.
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 frontend pods are not using the correct DNS name that includes the namespace. — Option C is correct because the frontend is in a different namespace and not using the fully qualified DNS name (backend-svc.backend-ns.svc.cluster.local) or the namespace is not properly configured for DNS resolution. Option A is wrong because the service type ClusterIP does not require a firewall rule. Option B is wrong because the StatefulSet is backed by a Service that provides DNS. Option D is wrong because network policy would cause timeout not connection refused.
What should I do if I get this PCD question wrong?
Identify which PCD exam domain this question belongs to, then review the specific concept being tested. Practise related questions in that domain and focus on understanding why each wrong answer is tempting — not just why the correct answer is right.
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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Question Discussion
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