CompTIA Exam Prep - ITF+, A+, Network+, Security+, CySA+

Every cloud contract contains a division of labor that most people only discover after something goes wrong. The shared responsibility model — also called the cloud responsibility matrix — is that division written down: which security tasks belong to the cloud service provider, and which remain yours. The provider secures the cloud. You secure what you put in it. Where the line falls depends entirely on the service model. It is the single most tested cloud security concept on CompTIA exams, and the reason is practical: the overwhelming majority of cloud breaches are customer-side misconfigurations, not provider failures. Understanding the line is what prevents assuming someone else is handling something nobody is handling. What Never Changes Regardless of service model, the provider is always responsible for the physical layer: data centers, physical access control, power, cooling, the host hardware, and the virtualization layer underneath your workloads. You cannot audit the...

Measured service — often called metered utilization or pay-as-you-go — is the billing model that makes cloud computing economically different from owning hardware. It is one of the five essential characteristics of cloud computing in the NIST definition, and it is the one that turns capital expenditure into operating expenditure. You pay for what you consume, measured continuously, with no commitment to capacity you are not using. Buying a server means paying for peak capacity forever, whether you use it at 3am on a Sunday or not. Metered utilization means the meter runs only while the resource does. That single shift is what makes rapid elasticity worth anything — releasing capacity saves nothing unless the bill follows it down. What Actually Gets Metered Compute — virtual machine time, usually per second or per hour, priced by instance size. Serverless functions bill per invocation and per gigabyte-second of execution, which can be dramatically cheaper for bursty workloads...

Rapid elasticity is one of the five essential characteristics of cloud computing in the NIST definition, and it is the one candidates most often confuse with scalability. They are related, but they are not the same thing, and exams test the difference directly. Rapid elasticity is the ability to add and remove capacity automatically, in minutes, in response to demand — and to stop paying for it the moment it is released. Elasticity Versus Scalability This distinction is worth getting straight before anything else, because it is the most commonly missed point on the topic. Scalability is about capability: can this system grow to handle more load? A system that can be expanded from 10 servers to 100 is scalable. Nothing in that word says how quickly, how automatically, or whether it can shrink back. Elasticity is about behavior: does capacity track demand automatically, in both directions, in near real time? An elastic system adds resources when load rises and, critically, r...