Backend & systems·Deployment, release and rollback
you ship the code turned off, switch it on for yourself, then for one percent, then for everyone.
Feature flag
Also calledfeature toggle, kill switch
A runtime switch controlling whether a code path is active. It separates release from deploy, enables gradual rollout, and gives you an instant off switch that does not require a deploy. Flags are debt: every one is a branch to test and understand, so each needs an owner and a removal date.