Google PCA Practice Question: Analyze and optimize technical and business processes
A company runs a web application on App Engine Standard environment. The application experiences downtime during deployments due to traffic shifting. Which two strategies should they implement to improve reliability? (Choose two.)
⚠ Common exam trap
Google Cloud often tests the distinction between deployment strategies (traffic splitting/version shifting) and scaling or API management features, leading candidates to confuse operational scaling fixes with deployment reliability improvements.
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 traffic splitting to gradually migrate traffic to the new version.
Option C is correct because App Engine traffic splitting lets you migrate user traffic to a new version gradually (for example, by IP address, cookie, or random percentage), so the new version can be validated with a small share of requests before full cutover, avoiding the all-at-once downtime caused by abrupt traffic shifting. Option D is correct because deploying the new code as a separate App Engine version keeps the currently serving version live and healthy, and then you shift traffic to the new version via the App Engine console or gcloud commands (such as gcloud app services set-traffic), which is the standard zero-downtime deployment pattern. Option A is not appropriate because Cloud Endpoints is an API management layer for authentication, monitoring, and quotas, not a mechanism for shifting App Engine version traffic during deployments. Option B is not appropriate because idle instances only reduce instance startup latency; they do not prevent downtime caused by traffic shifting between versions. Option E is not appropriate because manual scaling disables autoscaling and does not address the deployment traffic-shifting problem, and could actually reduce reliability under load.
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 Cloud Endpoints to manage API traffic and route deployments.
Why it's wrong here
Cloud Endpoints manages API authentication, quotas and monitoring; it does not control App Engine version traffic splitting, so it cannot prevent deployment downtime. It tempts because it sits in front of APIs and appears to route traffic, but version migration on App Engine is governed by traffic splitting and gradual rollout settings.
- ✗
Increase the number of idle instances to handle traffic during deployment.
Why it's wrong here
Idle instances are pre-warmed residents that reduce cold-start latency; they do not shift traffic between versions or prevent downtime during a deployment. It tempts because extra capacity sounds like resilience, but idle instances serve the same version, whereas the scenario requires gradual traffic migration to the new version.
- ✓
Use traffic splitting to gradually migrate traffic to the new version.
Why this is correct
Traffic splitting routes a configurable percentage of requests to the new version while the old version keeps serving the remainder. If the new version fails, traffic shifts back without downtime, satisfying the reliability requirement during deployments.
- ✓
Deploy to a separate version and then shift traffic using the App Engine console or gcloud.
Why this is correct
Deploying to a separate version keeps the new code inactive until it is verified, so no live traffic reaches it during build or startup. Traffic is then shifted via the console or gcloud, satisfying the requirement to avoid downtime caused by traffic shifting during deployment.
- ✗
Set manual scaling to avoid autoscaling delays.
Why it's wrong here
Manual scaling fixes instance counts, so App Engine cannot add capacity during a traffic shift, worsening the downtime. It tempts because removing autoscaling delays sounds like it stabilises deployments, but manual scaling is intended for predictable, steady workloads; the scenario needs gradual traffic migration across versions instead.
Go deeper
Related to this question
Learn chapter
Data Migration and Transfer Services
Key term
IP address
An IP address is a unique numerical label assigned to each device connected to a computer network that uses the Internet Protocol for communication.
Key term
App Engine
App Engine is a fully managed serverless platform from Google Cloud that lets developers build and deploy applications without worrying about the underlying infrastructure.
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
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.