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?
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
gcloud run services update-traffic allows traffic splitting between revisions.
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.
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
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