- can only have two treatment groups
- only use guardrail metrics
- have a variable allocation that lets you gradually roll out
- only use a sequential design where you see results continuously when the rollout is live
- It lets you ensure that the experience you are rolling out is not worsening the user experience before you roll it out to everyone.
- See comparisons between the group that has the feature you are rolling out and the group that has the current default experience for any metric.

