As scientific computing increasingly relies on diverse hardware (CPUs, GPUs, etc) and data structures, libraries face pressure to support multiple backends while maintaining a consistent API. This talk presents practical considerations for adding dispatching to existing libraries, enabling seamless integration with external backends. Using NetworkX and scikit-image as case studies, we demonstrate how they evolved to become a common API with multiple implementations, handle backend-specific behaviors, and ensure robustness through testing and documentation. We also discuss technical challenges, differences in approaches, community adoption strategies, and the broader implications for the SciPy ecosystem.