PCD Practice Question: Designing highly scalable, available, and reliable cloud-native applications
This PCD practice question tests your understanding of designing highly scalable, available, and reliable cloud-native applications. This is a configuration task: choose the command set that satisfies every stated requirement. Small differences — like 'secret' vs 'password' or 'transport input ssh' vs 'all' — change whether the answer is correct. 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.
A team is migrating a monolithic application to a microservices architecture on Google Kubernetes Engine (GKE). They want to ensure that failures in one microservice do not cascade to others. Which design pattern should they implement?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Implement a circuit breaker pattern that opens when failure thresholds are exceeded.
The circuit breaker pattern is the correct choice because it prevents cascading failures by monitoring inter-service calls and opening the circuit when failures exceed a threshold, allowing the system to fail fast and recover gracefully. In a GKE-based microservices architecture, this pattern is typically implemented using libraries like Resilience4j or Istio's circuit breaker, which can be configured to trip after a certain number of consecutive failures, thus protecting downstream services from being overwhelmed.
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.
✗
Implement retry logic with exponential backoff for all inter-service calls.
Why it's wrong here
Retries can exacerbate failures if the downstream service is overloaded.
✓
Implement a circuit breaker pattern that opens when failure thresholds are exceeded.
Why this is correct
Circuit breaker fails fast and prevents unnecessary load on failing services.
Related concept
Read the scenario before looking for a memorised answer.
✗
Use synchronous HTTP calls with timeouts to detect failures quickly.
Why it's wrong here
Synchronous calls can still cascade failures if not combined with circuit breakers.
✗
Use bulkheads to separate thread pools for each service.
Why it's wrong here
Bulkheads limit resource contention but do not prevent cascading failures.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Cisco often tests the distinction between patterns that isolate failures within a component (bulkheads) versus patterns that prevent failures from propagating across components (circuit breaker), leading candidates to confuse the scope of each pattern.
Detailed technical explanation
How to think about this question
The circuit breaker pattern operates in three states: closed (normal operation), open (failures exceed threshold, requests are immediately rejected), and half-open (after a timeout, a probe request is allowed to test recovery). In GKE, Istio's circuit breaker uses Envoy proxy's outlier detection, which can be configured with parameters like consecutive_5xx_errors and base_ejection_time to automatically eject unhealthy pods from the load balancing pool, providing a robust implementation at the service mesh level.
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.
Designing highly scalable, available, and reliable cloud-native applications — This question tests Designing highly scalable, available, and reliable cloud-native applications — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Implement a circuit breaker pattern that opens when failure thresholds are exceeded. — The circuit breaker pattern is the correct choice because it prevents cascading failures by monitoring inter-service calls and opening the circuit when failures exceed a threshold, allowing the system to fail fast and recover gracefully. In a GKE-based microservices architecture, this pattern is typically implemented using libraries like Resilience4j or Istio's circuit breaker, which can be configured to trip after a certain number of consecutive failures, thus protecting downstream services from being overwhelmed.
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.
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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