Five Key Concepts Concerning AWS Reserved Instances & Consolidated Billing

Reserved Instances offer AWS users an opportunity to dramatically reduce costs. However, properly calculating purchases, allocating costs, and calculating ROI is not easy. Here are five key ideas to help users perform those tasks and optimize their RI usage.
When evaluating RI purchases, it is probably best to start with the basics of using RI within a single account. RI function like coupons. For an upfront fee, the purchaser obtains compute access at discount for the term of the RI. This ‘coupon’ is not assigned to a specific resource. Instead, it is applicable to specific type of resource (defined by class, size, AZ, and platform). The constraint is one of time – a coupon can only be used once during any given hour.

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