Using LaunchDarkly To Target Personally Identifiable Information (PII) During Feature Flag Evaluation Without Leaking Sensitive Data

InVision uses LaunchDarkly as its feature flag service provider, which has significantly changed how teams think about feature deployment. One notable feature is the ability to mark certain user data as "private," allowing Personally Identifiable Information (PII) to be used in rule targeting without leaking beyond the application's boundaries. The most challenging aspect of using LaunchDarkly is understanding its user targeting mechanism, which involves syncing targeting rules with an application's local cache through asynchronous streaming. This approach enables designing targeting rules that depend on information only known by the client, such as email addresses marked as private. By denoting specific fields as "private," LaunchDarkly allows for safe targeting of PII while ensuring data security and compliance with privacy regulations.