This week is about money. One of the cloud's biggest draws is "you pay only for what you use" — but in fact, the very same resource can cost dramatically different amounts depending on how you purchase it. Today we'll organize the compute pricing models centered on EC2 — On-Demand, Reserved Instances (RIs), Savings Plans, and Spot — along with the Free Tier for new users and volume discounts that lower your unit price the more you use.
There's one core question: "How long, and how predictably, does this workload run?" The answer to that determines the cheapest way to buy.
On-Demand is the most basic pricing model