Facebook's engineering success is attributed to their "Move Fast With Stable Infra" approach and the in-house system called Gatekeeper. This system allows them to quickly iterate features based on feedback, separate deployment from rollout, and maintain stability. Key components of this strategy include internal usage for quick feature feedback, staged rollouts, dynamic configuration, right hand side units for microservices, shadow production for load testing, data-informed decisions, advance country launches, and soft launches. By using feature flags and Gatekeeper, Facebook can quickly isolate the impact of a change, make data-informed decisions, and control user visibility.