A gradual rollout is the habit of proving a release with a small slice of real traffic before expanding it. The goal is not to move slowly. The goal is to keep the blast radius small while you learn from production.
With feature flags, the deployment can already be live while the rollout is still at 1%. That gives engineering and product teams a controlled way to move forward.
Choose a stable rollout key
Percentage rollouts need stable bucketing. The same user should keep getting the same result as long as the percentage does not change.
Use a durable identifier such as user ID, account ID, tenant ID, or organization ID depending on the behavior you are releasing.
Start with a small cohort
- 0%: deploy the code behind the flag.
- 1%: verify real production behavior.
- 10%: look for error, latency, and conversion changes.
- 50%: check scale effects and support volume.
- 100%: complete the release and schedule cleanup.
Measure before expanding
Gradual rollout is only useful when each step has a decision point. Look at application errors, latency, user feedback, and product metrics before increasing exposure.
If the signal is unclear, keep the percentage steady. If the signal is bad, turn the flag down or off and investigate from a smaller blast radius.
Keep rollback boring
The rollback path should be the same button or API call used for rollout. Do not rely on a new deployment to stop a bad release.
Related docs
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