What is a cloud service?

As part of this introduction, let's define the terminology to make sure we are all on the same page.

The National Institute of Standards and Technology (NIST) defines cloud as a technology that has the following five characteristics:

• On-demand self-service: Imagine you wish to open a blog and you need compute resources. Instead of purchasing hardware and waiting for the vendor to ship it to your office and having to deploy software, the easier alternative can be a self-service portal, where you can select a pre-installed operating system and content management system that you can deploy within a few minutes by yourself.
• Broad network access: Consider having enough network access (the type that large Internet Service Providers (ISPs) have) to serve millions of end users with your application.
• Resource pooling: Consider having thousands of computers, running in a large server farm, and being able to maximize their use (from CPU, memory, and storage capacity), instead of having a single server running 10% of its CPU utilization.
• Rapid elasticity: Consider having the ability to increase and decrease the amount of compute resources (from a single server to thousands of servers, and then back to a single server), all according to your application or service needs.
• Measured service: Consider having the ability to pay for only the resources you consumed and being able to generate a billing report that shows which resources have been used and how much you must pay for the resources.

Further details relating to the NIST definition can be found at the following link:

https://nvlpubs.nist.gov/nistpubs/Legacy/SP/nistspecialpublication800-145.pdf