The origin of cloud development for the leading CSPs stems from the pain of managing monolithic systems. As each company (Amazon.com retail site, Google.com's indexing of the web) was experiencing tremendous growth, the traditional IT systems were incapable of keeping up with the rate of expansion and evolving at a necessary pace to enable the innovation that was needed. This story is true and well-documented in the public sphere for both AWS and GCP. As their internal systems matured around these services (provided initially as internal only to product development teams), Amazon took the step to provide these services to external customers on a utility-based billing system.

Many businesses and architects now see the virtue in this decoupling process, calling the fully decoupled environment a service-oriented architecture (SOA). We define SOAs as digital environments where each constituent system providing the lowest level of application functionality is run independently and interacts with other systems solely through APIs. In practice, this means each service is deployed and managed independently (ideally as a stack managed by IaC). Services can be dependent upon other services; however, this exchange of data is accomplished through APIs.

SOAs and microservices are at the mature end of the CNMM for scalability and availability. Decoupling your application or IT environment requires years of work and technical discipline.