Percentage-Based Feature Rollout

Percentage-Based Rollout

A percentage rollout releases a feature to a fraction of your user base. Instead of an all-or-nothing launch, you incrementally increase the percentage while monitoring for issues.

Configuration Example

{
  "new-checkout-flow": {
    "name": "New Checkout Flow",
    "description": "Redesigned checkout experience with fewer steps",
    "type": "boolean",
    "enabled": true,
    "defaultValue": false,
    "targeting": [
      {
        "type": "percentage-rollout",
        "percentage": 10
      }
    ]
  }
}

How Percentage Hashing Works

The percentage is not random on each request. Instead, the user's ID is hashed to produce a consistent bucket number between 0-99. If a user falls in bucket 0-9 (for a 10% rollout), they see the feature. This ensures the same user always gets the same experience.

Recommended Rollout Schedule

Phase	Percentage	Duration	Purpose
Canary	1-2%	1-2 hours	Catch critical bugs
Early	5-10%	1-2 days	Monitor performance metrics
Mid	25-50%	3-5 days	Validate at scale
Wide	75-90%	2-3 days	Final validation
Full	100%	Permanent	Complete rollout

Unleash Strategy

In Unleash, this uses the gradualRolloutUserId strategy with a percentage parameter and a groupId for consistent bucketing.

Monitoring Tips

• Track error rates by flag variation (on vs off)
• Compare page load times between groups
• Monitor conversion rates if the feature affects a funnel
• Set up alerts for anomalies in the feature-on group