The Courier notification system offers a lightweight solution using React that has a global state and runs independently in the background. This allows teams to render the components regardless of their tech stack. The components are built using custom Courier components inspired by Web Components, which enable a modular setup for a custom solution that can be implemented anywhere with any specific user interface or front-end library or framework. The initial setup is straightforward, and additional configuration options allow for deferring initialization and mapping configuration for each component. The SDK is exposed on window.courier and is loaded asynchronously. After initialization, the Courier components render into a portal, preserving global state, and can be dynamically imported using React Suspense to ensure small bundle size.