Curve, a London-based fintech startup, recently built a peer-to-peer payments feature called "Curve Send." The team wanted to do a phased rollout of the feature rather than a "big-bang" release. They faced challenges in creating reliable user segments due to social dependencies of the feature, which required participation from both sender and recipient. Curve used LaunchDarkly feature flags to execute a successful phased rollout of the peer-to-peer payments feature. The team learned that when rolling out features with complex dependencies, it's crucial to have fine-grained control over users and ensure that both parties involved in the interaction have access to the feature at the right time.