What is a “feature flag”?

Question

High Scalability mentions feature flags here:

5 things toxic to scalability, \"5. Lack of Feature Flags\"

What exactly are feature flags?

Answer 1

At my company we used to have an own solution for that. We created a service providing a downloadable config (.json) file for every apps. In that config we stored the flags for the features. Based on that config the app can show or hide the current feature. (For example show or hide a menu item on the sidebar).

We also created an internal admin page where we can configure the feature-flags. It worked quite good for a while but after that we would have liked to do user targeting and A/B testing. To develop by own It seemed too much effort, so we chose a third-party solution. As already mentioned here there are many solutions for that.

We chose ConfigCat because it supports customized target groups and percentage-based rollout at once. You can check the supported open-source sdks on github.