Google ACE Practice Question: Ensuring Successful Operation of a Cloud Solution

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 services update-traffic my-service --to-revision new-revision --percent 10

  Why this is correct

  The `gcloud run services update-traffic` command is the correct tool for modifying an existing Cloud Run service's traffic routing. By specifying `--to-revision new-revision` and `--percent 10`, you instruct the service to send 10% of incoming requests to that revision while the remaining 90% continues to the current default revision. This enables incremental canary rollouts and rollbacks without redeploying code.

• ✗

  gcloud run revisions traffic my-service --to-revision new-revision --percent 10

  Why it's wrong here

  The `gcloud run revisions traffic` command does not exist; the `gcloud run revisions` group only manages revision lifecycle operations such as listing and describing. Traffic routing is a service-level setting, not a revision-level one, so it must be adjusted with `gcloud run services update-traffic`. Running this command will fail with a usage error because `traffic` is not a recognized subcommand of `gcloud run revisions`.

• ✗

  gcloud run services update my-service --image gcr.io/my-project/my-image:new

  Why it's wrong here

  The `gcloud run services update` command with the `--image` flag deploys a new revision, but it does not let you explicitly control the percentage of traffic that revision receives. This command shifts traffic according to the service's deployment strategy, typically all or nothing, and cannot specify a 10% slice to a particular revision. To set a precise traffic percentage to a named revision, `gcloud run services update-traffic` is required.

• ✗

  gcloud run deploy my-service --image gcr.io/my-project/my-image:new --traffic new-revision=10

  Why it's wrong here

  The `gcloud run deploy --traffic` flag is intended for the initial deployment of a service, not for adjusting traffic on an existing service. When used on a service that already exists, it does not reliably set 10% of traffic to `new-revision` because it triggers a new deployment and may reset the traffic configuration. The recommended way to change the split on a live service is `gcloud run services update-traffic`.

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