Path-breaking technologies are emerging and evolving fast toward digital innovation, disruption, and transformation. A variety of breakthroughs are being unearthed and popularized in order to bring in a variety of acceleration, automation, and augmentation in IT and business spaces. We are being bombarded with a number of application architectures, ranging from service-oriented architecture (SOA), event-driven architecture (EDA), and resource-oriented architecture (ROA) to MSA. Containers have become the default runtime for services. Cloud servers are being expressed and exposed as a collection of containers. With the surging popularity of container-orchestration platforms, creating container clusters and using them to run software applications and services has become the most prominent way to develop, deploy, and manage software. The cool convergence, as explained elsewhere in this book, between containers and microservices has propelled the next generation of application delivery. Each microservice is being fitted with one or more APIs. Further on, each microservice has its own data store. For data security and effective data management, each database is also being given an API to perform data operations with confidence and clarity.

The other prominent advancements are the faster proliferation of cloud environments and the fact that each cloud center is being stuffed with thousands of applications and platforms. Cloud-hosted platforms enable third-party application developers not only to develop newer applications, but also facilitate a seamless and spontaneous integration with their applications. As we are heading toward federated cloud environments to create composite applications, APIs emerge as the most crucial entity toward fulfilling the fast-emerging multi-cloud idea. Device-to-device (D2D), device-to-cloud (D2C), and cloud-to-cloud (C2C) integration gets facilitated through APIs.