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Google ACE Practice Question: A company runs an App Engine Standard application…
A company runs an App Engine Standard application with multiple versions. They want to gradually roll out new features by sending a small percentage of traffic to a new version. How should they implement this?
⚠ Common exam trap
Many exam-takers confuse App Engine's internal traffic splitting with external Cloud Load Balancing, thinking they need to set up a separate load balancer when App Engine already provides this capability natively for version-level traffic distribution.
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 App Engine's traffic splitting feature to assign a percentage of traffic to the new version
App Engine Standard provides built-in traffic splitting, allowing you to assign a percentage of incoming requests to different versions of the same service. This is the simplest and most direct way to gradually roll out a new feature by sending a small percentage of traffic to the new version without needing external load balancers or additional services.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Deploy the new version and delete the old version
Why it's wrong here
This approach forces an abrupt cutover: once the old version is deleted, App Engine routes 100% of traffic to the new version, eliminating any ability to roll back or compare in production. It also bypasses App Engine's gradual migration features entirely, making it an all-or-nothing deployment rather than a controlled incremental rollout.
- ✗
Use Cloud Load Balancing to distribute traffic between versions
Why it's wrong here
App Engine standard already includes managed load balancing and traffic routing at the service/version level; an external Cloud Load Balancing setup cannot assign weights to individual versions inside a single App Engine service. Adding a load balancer only fronts the app's URL and gives no finer control over version traffic, so it would not accomplish a gradual rollout.
- ✗
Create a new service for the new version and use a custom domain
Why it's wrong here
Creating a separate App Engine service and pointing a custom domain to it treats the new version as an isolated environment, not as a version within the same service. App Engine's 'service' abstraction is for separating responsibilities, not for incrementally shifting traffic between code versions; you'd need to manually configure dispatch rules or update DNS, which does not provide percentage-based gradual rollout.
- ✓
Use App Engine's traffic splitting feature to assign a percentage of traffic to the new version
Why this is correct
App Engine's traffic splitting feature lets you specify a percentage of traffic to route to each version of a service, using either a cookie-based or IP-based (or random) split. You can start by sending, say, 5% of requests to the new version, monitor error rates and latency, then gradually increase that percentage while keeping the old version available for instant rollback.
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Google Compute Engine
Key term
Service
A service is a software component or system that performs a specific function and is available to be used by other programs or users over a network.
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
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