- A
Use an HTTP(S) load balancer with a backend service configured with a health check and enable connection draining.
HTTP(S) LB with health checks automatically reroutes traffic; connection draining adds graceful shutdown.
- B
Use an internal load balancer with a backend service configured with a health check.
Why wrong: Internal LB is for internal traffic, not external users.
- C
Use a network load balancer with a health check configured on the target pool.
Why wrong: Network LB is for TCP/UDP traffic, less application-aware.
- D
Use an HTTP(S) load balancer with a backend service configured with a health check and enable session affinity.
Why wrong: Session affinity ties clients to specific instances, which can cause traffic to unhealthy instances.
- E
Use a TCP proxy load balancer with a backend service configured with a health check.
Why wrong: TCP proxy works but is not ideal for HTTP applications.
Google PCA Ensure solution and operations reliability Practice Question
This PCA practice question tests your understanding of ensure solution and operations reliability. 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.
A company is deploying a critical application on Compute Engine with an HTTP load balancer. They want to ensure that if an instance health check fails, traffic is automatically rerouted to healthy instances. Which configuration should they implement?
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
Use an HTTP(S) load balancer with a backend service configured with a health check and enable connection draining.
Option A is correct because an HTTP(S) load balancer with a backend service configured with a health check automatically monitors instance health and reroutes traffic away from unhealthy instances. Enabling connection draining ensures that in-flight requests to an unhealthy instance are given time to complete before the instance is removed from the load balancing pool, preventing disruption to active sessions.
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.
- ✓
Use an HTTP(S) load balancer with a backend service configured with a health check and enable connection draining.
Why this is correct
HTTP(S) LB with health checks automatically reroutes traffic; connection draining adds graceful shutdown.
Related concept
Read the scenario before looking for a memorised answer.
- ✗
Use an internal load balancer with a backend service configured with a health check.
Why it's wrong here
Internal LB is for internal traffic, not external users.
- ✗
Use a network load balancer with a health check configured on the target pool.
- ✗
Use an HTTP(S) load balancer with a backend service configured with a health check and enable session affinity.
Why it's wrong here
Session affinity ties clients to specific instances, which can cause traffic to unhealthy instances.
- ✗
Use a TCP proxy load balancer with a backend service configured with a health check.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Google Cloud often tests the distinction between connection draining and session affinity, where candidates mistakenly think session affinity is needed for failover, but in reality session affinity prevents rerouting and should be avoided for high-availability scenarios.
Detailed technical explanation
How to think about this question
Under the hood, the HTTP(S) load balancer uses a global anycast IP and a Google Front End (GFE) to distribute traffic across backend instances in multiple regions. Health checks are sent from the GFE to the instance's health check endpoint (e.g., /healthz) at configurable intervals (default 5 seconds), and if an instance fails a configurable number of consecutive checks (default 2), it is marked unhealthy and removed from the backend service's rotation. Connection draining, when enabled, sets a timeout (default 60 seconds) during which existing connections to the unhealthy instance are allowed to finish before the instance is fully drained.
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
An e-commerce site experiences heavy traffic on Black Friday and near-zero traffic during off-peak weeks. Rather than provisioning permanent large VMs, the team uses auto-scaling groups that add capacity automatically under load and reduce it overnight. Questions like this test whether you understand elasticity, availability zones, and cloud compute scaling patterns.
What to study next
Got this wrong? Here's your next step.
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FAQ
Questions learners often ask
What does this PCA question test?
Ensure solution and operations reliability — This question tests Ensure solution and operations reliability — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Use an HTTP(S) load balancer with a backend service configured with a health check and enable connection draining. — Option A is correct because an HTTP(S) load balancer with a backend service configured with a health check automatically monitors instance health and reroutes traffic away from unhealthy instances. Enabling connection draining ensures that in-flight requests to an unhealthy instance are given time to complete before the instance is removed from the load balancing pool, preventing disruption to active sessions.
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.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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Last reviewed: Jun 30, 2026
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