Google PCA Ensure solution and operations reliability Practice Question
A healthcare analytics company runs a stateless API on a regional managed instance group behind an external Application Load Balancer. The SRE team wants to improve reliability and reduce customer-visible errors during zonal and instance failures. (Choose two.)
⚠ Common exam trap
The trap here is reaching for regional expansion or caching when the stated failure domain is zonal and instance-level, where autoscaling and accurate health checking are the targeted fixes.
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
✓
Configure the load balancer's backend service with a health check that matches the API's readiness endpoint and set a sensible unhealthy threshold.
Autoscaling lets the regional managed instance group add or maintain capacity so healthy instances in surviving zones can handle traffic when one zone or instance fails. A health check aligned to the API's readiness endpoint ensures the load balancer routes only to instances that can actually serve requests, cutting customer-visible errors. Together they address zonal and instance failure reliability.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Set the load balancer's balancing mode to RATE and configure a maximum rate per instance to cap traffic.
Why it's wrong here
RATE balancing with a maximum rate per instance can distribute load predictably, but capping the rate does not add capacity or improve recovery from instance or zonal failure. If anything, a hard cap can cause the load balancer to drop or reject traffic once the limit is reached, increasing errors. It is a traffic-shaping control, not a reliability improvement for the failure scenarios described.
- ✓
Configure the load balancer's backend service with a health check that matches the API's readiness endpoint and set a sensible unhealthy threshold.
Why this is correct
An accurate health check lets the load balancer stop sending traffic to instances that cannot serve requests, so users are routed only to healthy backends. Matching the readiness endpoint ensures the check reflects real application health rather than just port availability. This reduces customer-visible errors during instance failures and is a core reliability practice for load-balanced stateless services.
- ✓
Enable autoscaling on the managed instance group based on CPU utilization and load balancing capacity.
Why this is correct
Autoscaling adjusts the number of instances to match demand, so remaining healthy instances in other zones can absorb traffic when one zone degrades. Scaling on load balancing capacity specifically responds to the request load reaching the backend, which helps maintain headroom and reduces errors during spikes or partial capacity loss. This directly improves reliability for a stateless API behind the load balancer.
- ✗
Create a second managed instance group in a different region and add it as a backend to the same load balancer.
Why it's wrong here
Adding a cross-region backend does improve regional resilience, but the scenario specifies a regional managed instance group and asks about zonal and instance failures. A regional MIG already spreads instances across zones within the region, so this option addresses a broader failure domain than the stated goal and adds complexity. It is not one of the two targeted improvements for zonal and instance-level reliability.
- ✗
Enable Cloud CDN on the backend service to cache API responses and reduce origin load.
Why it's wrong here
Cloud CDN caches cacheable content at edge locations, which helps static assets or idempotent GET responses, but a healthcare analytics API typically returns personalized or sensitive data that should not be cached. Caching could introduce stale or privacy-compromised responses. It does not address instance or zonal failure recovery, so it is not an appropriate reliability measure here.
Go deeper
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Key term
Load balancer
A load balancer is a device or software that distributes incoming network traffic across multiple servers so no single server gets overwhelmed.
Key term
Managed instance group
A managed instance group is a collection of identical virtual machine instances that are automatically managed as a single unit to ensure high availability and scalability.
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JA
Written and reviewed by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
Last reviewed September 2026 · checked against the official Google Cloud exam blueprint
This PCA practice question is part of Courseiva's free Google Cloud certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the PCA exam.