Technology is moving towards modern digital systems with business functionality exposed by integrating multiple best-of-breed software systems. In today's interconnected digital landscape, application programming interfaces (APIs) are the backbone of enterprise applications, enabling seamless data exchange and service integration.This book takes you through the entire API lifecycle, starting with the evolution of APIs and moving beyond traditional REST to modern architectures like GraphQL and gRPC. You will learn the core principles of API design, including best practices, security protocols, and open standard adoption like OpenAPI. You will also gain practical skills in API development, testing, and documentation, focusing on enhancing developer experience and ensuring scalability. Crucial aspects of API governance, real-time API implementation, and API gateways are thoroughly covered. Finally, the book explores emerging trends, including generative AI APIs, vision, natural language processing (NLP), speech, and large language models (LLMs), preparing you for the future of API integration.By the end of this book, you will gain the expertise to confidently build and manage APIs for enterprise applications, becoming a proficient architect in the dynamic world of digital integration, ready to leverage APIs as a powerful strategic asset.