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Maven / GitHub Actions Interview Questions

How do you use concurrency groups to cancel outdated workflow runs in GitHub Actions?

The concurrency: key limits how many workflow runs (or jobs) with the same group name can be active simultaneously. Setting cancel-in-progress: true automatically cancels any run in the same group that is already in progress when a new one starts — perfect for preventing stacked deploys or redundant CI runs on fast-pushed branches.

# Cancel any previous CI run on the same branch when a new commit is pushed
concurrency:
  group: ci-${{ github.ref }}
  cancel-in-progress: true

jobs:
  test:
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@v4
      - run: npm test

The group: string is the identifier. Runs sharing the same group string compete for the single-active-run slot. Using ${{ github.ref }} scopes the group to a branch, so pushes to main only cancel each other, not pushes to feature branches.

For deployment workflows you often want a different policy: queue new runs rather than cancel them, and never cancel a run that is already deploying. Achieve this by omitting cancel-in-progress (defaults to false):

concurrency:
  group: deploy-${{ github.ref }}
  # cancel-in-progress defaults to false → runs are queued, not cancelled

Concurrency can also be set at the job level (not just workflow level) to limit parallelism for a specific job such as a deployment job while leaving other jobs unaffected.

jobs:
  deploy:
    concurrency:
      group: deploy-production
      cancel-in-progress: false
What does cancel-in-progress: true do in a GitHub Actions concurrency group?
How would you scope a concurrency group so pushes to different branches do not cancel each other?

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