In thinking about a cloud computing definition, we have to consider the five characteristics that the National Institute of Standards and Technology (NIST) outline as an essential part of any cloud system:
- Broad Network Access: This characteristic is common with other models and simply means that cloud services require networked connections between backend infrastructure (such as servers and storage) and frontend clients (such as laptops or smartphones).
- Resource Pooling: In many cases, this involves virtualized resources, but in some cases, physical resources themselves are pooled together with a layer of software.
- Rapid Elasticity: Here cloud computing services begin to drastically separate from other models. Rather than simply grouping resources into static pools, cloud resources can dynamically grow and shrink depending on the workload demands.
- On-Demand Self-Service: In contrast to other models that require significant technical expertise to spin up, cloud services have simple methods that allow users with relatively limited technical skills to create or access resources.
- Measured Service: Given the dynamic nature of cloud computing, the final characteristic is the ability to measure exactly how much resource is being used, which leads to the ability to charge for exact usage rather than purchasing or renting for a broad period of time.
Initially, companies only leveraged some of the unique characteristics. For instance, a company may have migrated some on-premises applications to a cloud provider, offloading the maintenance work needed for local servers. Over time, companies have begun exploring the more advanced aspects of cloud computing, using flexible development environments to build new applications or implement robust storage solutions.