Decide who takes part. Keep full control of your rollouts.
A gate sits in front of the experiment and answers one question before anything else runs: is this visitor in the optimization group or not? Set rules and rollout stages to keep full control.
Same evaluation the gate runs on the hot path — never a separate preview.
Try it on a cohort first. Then roll out gradually.
Keep control of the optimization along the way.
One number, from one percent to everyone.
Change the rollout in the console and every replica picks it up within seconds — no deploy, no restart, no release train. Turn it up while it is working; turn it down when you need to.
Turning it up never reshuffles anyone.
Whether a visitor takes part is worked out from the id you send, not a coin flip. Someone who saw the new checkout yesterday sees it again today — and raising the rollout only ever adds people.
No row ever goes back. That is the whole guarantee — and the reason the numbers you read at the end mean something.
Manage targeting rules using your own data.
Anything you send with a request can become a rule — your own plan names, your own cohorts, nothing registered in advance. Rules are read top to bottom, and the first one that matches decides.
Rules run only for visitors the rollout has already let in. Everyone the rollout has not reached yet sees your current version regardless.
Undoing it is a number, not a rollback.
Set the rollout to zero and everyone is back on your current version. No revert, no release to wait for — and everything the experiment learned is still there when you turn it back up.
Forty in every hundred are seeing the new checkout. It is working, and then it isn’t.
Everyone is on your current version again, within seconds.