Feature flags are a powerful tool for Node.js development, offering developers the ability to control functionality, test features safely, and iterate quickly without impacting production environments. The article provides a step-by-step guide to creating a simple library API using Node.js and Express, illustrating how feature flags can separate code deployment from feature enablement. By using Split's JavaScript SDK, developers can easily manage which features are available to users, allowing for safe experimentation and deployment of new functionalities. The use of feature flags is demonstrated through enabling and disabling a book deletion feature, showing how developers can control user access based on treatment settings within Split. The guide emphasizes the flexibility and control feature flags offer in software development, encouraging developers to explore advanced options for experimentation and secure deployment.