It's homegrown. This paper talks about it: https://research.facebook.com/file/877841159827226/holistic-configuration-management-at-facebook.pdf https://research

It's homegrown. This paper talks about it: https://research.facebook.com/file/877841159827226/holistic-configuration-management-at-facebook.pdf https://research.facebook.com/file/877841159827226/holistic-... It also mentions Gatekeeper, which is the rule-based engine I mentioned built on top of it, but there are other feature flag solutions that use configerator for different use cases like killswitches or gradual rollout.