Google ACE Practice Question: Ensuring Successful Operation of a Cloud Solution
You are using Cloud Run and want to split traffic so that 10% of requests go to revision v2 and 90% go to revision v1. Which command should you use?
⚠ Common exam trap
ACE often tests the exact gcloud command syntax for traffic splitting; candidates may confuse `gcloud run deploy` with `gcloud run services update-traffic`, or use incorrect flags like `--traffic` instead of `--to-revisions`.
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
✓
gcloud run services update-traffic --to-revisions v1=90,v2=10
The correct command to split traffic between Cloud Run revisions is `gcloud run services update-traffic` with the `--to-revisions` flag, specifying the revision names and percentages. This command updates the traffic allocation for a service. The syntax `--to-revisions v1=90,v2=10` correctly assigns 90% to v1 and 10% to v2.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
gcloud run deploy --image my-image --traffic v1=90,v2=10
Why it's wrong here
This tries to pass `--traffic` to `gcloud run deploy`, but that command doesn't expose a `--traffic` flag for assigning per-revision percentages. Deploying creates and tags a new revision; you would either leave it untrafficked with `--no-traffic` or use the separate `update-traffic` command to perform the split. Therefore the command as written is not valid for setting the 90/10 routing.
- ✗
gcloud run services update --traffic v1=90,v2=10
Why it's wrong here
Although `gcloud run services update` can change service-level settings such as concurrency, timeout, and environment variables, it does not accept a `--traffic` flag for routing percentages. The only correct way to adjust a traffic split across existing revisions is the dedicated `gcloud run services update-traffic` subcommand, which uses `--to-revisions` to list revision=percentage pairs. Passing `--traffic` here would be unrecognized and the update would fail.
- ✗
gcloud run revisions update v2 --traffic 10
Why it's wrong here
There is no `gcloud run revisions update` subcommand, and revisions are immutable once created, so you cannot modify a revision's own traffic weight. Traffic percentages are a property of the service's routing configuration, not of the revision object. To adjust the split you must invoke the service-level `update-traffic` command referencing the existing revision names.
- ✓
gcloud run services update-traffic --to-revisions v1=90,v2=10
Why this is correct
This is the correct command for splitting traffic between already deployed revisions: `gcloud run services update-traffic` with `--to-revisions` takes a comma-separated list of `revision=percentage` pairs (v1=90,v2=10) and applies the routing immediately. The specified revisions must exist and the percentages must total 100. It does not create a new revision, so it is the appropriate operation after v1 and v2 have both been deployed.
Go deeper
Related to this question
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Packet Mirroring and Traffic Analysis
Key term
Cloud Run
Cloud Run is a fully managed compute platform from Google Cloud that lets you run containerized applications in a serverless environment, automatically scaling from zero to thousands of requests.
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.
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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 ACE 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 ACE exam.