Roll out a feature with a flag
Turn a feature on for some users and change it while the app runs.
Preview
Status Status is where the work is: Planned (in a milestone, not started), Building (tickets in progress), Preview (usable, may change), then the stability it ships at.
Stability The promise an interface ships with.
- Stable Follows semantic versioning; breaking changes need a new major, 12 months of overlap and a codemod.
- Beta Usable in production; may change before it becomes stable.
- Experimental May change or go away; needs an explicit opt-in in main.yaml.
You will add a flag, check it in code and change it with no deploy. It takes about 10 minutes.
You need
- A config store (see Change config without a deploy).
1. Define the flag
Set flags.new-checkout in your config store:
{ "enabled": true, "rollout": 10 }2. Check it
import { flags } from "mainsdk";
export function checkoutFor(userId: string) {
const rows = flags.value("export.row-limit", 500, { user: userId });
return flags.enabled("new-checkout", { user: userId }) ? { checkout: "new", rows } : { checkout: "classic", rows };
}The check reads memory only, and the same user gets the same answer on every instance.
3. Change it live
Set rollout to 50, or enabled to false. Every instance applies it with no restart, and the change is audited.
Check it worked
About 10 percent of users see the new checkout, and setting enabled: false turns it off for everyone.
Next
- Feature flags
- Plans and entitlements: for features a plan includes.
Was this page helpful?