How do you design feature flags?
The point
A feature flag is a switch that lets you ship code in a release turned off and enable it later without a new build: gradual rollout, A/B tests, a kill switch for a misbehaving feature, different configurations for QA. Sources: remote config (Firebase Remote Config, your own backend), a local override for a debug menu, a default value in code.
The rest of this answer, with code and interview follow-ups, is in the DevPrep app.
Read the full answer in DevPrep