Feature flag

A feature flag is a switch in your code that turns a feature on or off without deploying new code. You wrap the new behaviour in a condition, ship it to production turned off, then flip it on for yourself, a few beta customers, or everyone, all from a config setting. For a lean founder this decouples deploying from releasing, which is quietly powerful. You can merge half-finished work safely, run a feature for one client to test it live, and kill a broken feature instantly instead of scrambling to roll back a deploy. Flags also enable gradual rollouts: switch a feature on for 10% of users, watch for errors, then ramp up. The cost is discipline, every flag is a branch in your logic, so you remove flags once a feature is fully shipped rather than letting them pile up into permanent clutter.