Monolithic and massive applications are being modernized and migrated to cloud environments in order to reap all the originally envisaged benefits of the cloud computing model. Microservices are emerging as the most optimized building block to produce enterprise-scale applications. Not only for development but also for application modernization, microservices are being touted as the most suitable approach. That is, legacy applications are being systematically partitioned into multiple interoperable, portable, publicly discoverable, network accessible, reusable, composable, fine grained, technology-agnostic, containerized, horizontally scalable, and independently deployable microservices. The point here is that every microservice exposes one or more interfaces. RESTful interfaces are the most popular ones for microservices to connect and compose bigger and better services. Microservices are therefore typically RESTful services. Thus, application refactoring and remediation are being sped up and streamlined through RESTful services and their APIs. Service, application and data integration, and orchestration happen through RESTful APIs.

In short, new technologies and toolkits, programming and script languages, architecture and design patterns, integrated platforms, pioneering algorithms, enabling frameworks, composable and clustered infrastructures, optimized processes, fresh building blocks, data formats, and protocols are constantly emerging and impacting the discipline of software engineering. Agile software development methodologies are getting the importance to build applications quickly. Besides, the role and responsibility of microservices is increasingly felt in realizing enterprise-scale applications. That is, besides agile techniques, microservices contribute immensely to the rapid development of applications. In other words, applications are being readied instantaneously by compositing multiple microservices.

Applications are mainly interdependent. They can't work in isolation. They have to be integrated dynamically to offer users an integrated experience. Applications also have to be linked up with other applications, data sources and stores, data processing and data analytics platforms, and messaging and middleware systems. Thus, the inescapable integration has to happen via well-intended and designed APIs. Finally, legacy applications have to be dismantled into easily manageable and loosely coupled modules. These modular components, in conjunction with management solutions, will significantly enhance their utilization, efficiency, visibility, and controllability. Further on, on a per-need basis, several modules can be picked up and combined to create bigger and better applications.