FIGURE 1.2 Copies of a machine image are added to new VMs as they're launched.

      AWS offers its autoscaling service through which you define a machine image that can be instantly and automatically replicated and launched into multiple instances to meet demand.

      Elasticity

      The principle of elasticity covers some of the same ground as scalability—both address how the system manages changing demand. However, though the images used in a scalable environment let you ramp up capacity to meet rising demand, an elastic infrastructure will automatically reduce capacity when demand drops. This makes it possible to control costs, since you'll run resources only when they're needed.

      Cost Management

      Besides the ability to control expenses by closely managing the resources you use, cloud computing transitions your IT spending from a capital expenditure (capex) framework into something closer to operational expenditure (opex).

      In practical terms, this means you no longer have to spend $10,000 up front for every new server you deploy—along with associated electricity, cooling, security, and rack space costs. Instead, you're billed much smaller incremental amounts for as long as your application runs.

      That doesn't necessarily mean your long‐term cloud‐based opex costs will always be less than you'd pay over the lifetime of a comparable data center deployment. But it does mean you won't have to expose yourself to risky speculation about your long‐term needs. If, sometime in the future, changing demand calls for new hardware, AWS will be able to deliver it within a minute or two.

      To help you understand the full implications of cloud compute spending, AWS provides a free Total Cost of Ownership (TCO) Calculator at aws.amazon.com/tco-calculator. This calculator helps you perform proper “apples‐to‐apples” comparisons between your current data center costs and what an identical operation would cost you on AWS.

The AWS Cloud

Keeping up with the steady stream of new services showing up on the AWS Console can be frustrating. But as a solutions architect, your main focus should be on the core service categories. This section briefly summarizes each of the core categories (as shown in Table 1.1) and then does the same for key individual services. You'll learn much more about all of these (and more) services through the rest of the book, but it's worth focusing on these short definitions, because they lie at the foundation of everything else you're going to learn.

TABLE 1.1 AWS service categories

Table 1.2 describes the functions of some core AWS services, organized by category.

TABLE 1.2 Core AWS services (by category)