The 4-Way Compute Tradeoff: Reserved vs Spot vs Savings Plan vs On-Demand After 3 Years of FinOps Data

Three years of cost retrospectives across mixed AWS fleets keep landing on the same finding. Teams that pick one compute commitment model and apply it across the whole fleet (all-Savings-Plan, all-On-Demand, all-Spot for the brave ones) overspend the optimum by 18 to 35 percent. The single-model decision is comfortable because it is one decision; the portfolio decision is uncomfortable because it is four decisions. Three years of data says the four-decision answer is worth the discomfort. The po