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I don't think they are easy to reason about. They're non-trivial to explain, and to figure out how to make best use of them requires quite a lot of modelling, u

I don't think they are easy to reason about. They're non-trivial to explain, and to figure out how to make best use of them requires quite a lot of modelling, usage projection, etc, to figure out how many of each type to buy. The lowest priced options also require pre-purchasing, which ties up cash. They're rarely worth it for a business with typical cash flow. From a cash flow perspective "it just gets cheaper after 3 months" is very straightforward, requires no usage projection, and not a lot of modelling to figure out eventual prices. The fact that it's not opt-in also means that more businesses will get the benefits, so many don't use the reserved instances because they don't have the capacity to figure out how best to use them, or worry about giving up the flexibility.

acdha 4y ago
> The lowest priced options also require pre-purchasing, which ties up cash. They're rarely worth it for a business with typical cash flow. This is probably where our experiences differ: I’ve dealt with this at large organizations where cash flow isn’t tight and the accountants have never had trouble working with the prepayment concept since they do that for tons of things.
- danpalmer 4y ago
  That's fair, but cash flow is a major focus for many businesses, and with AWS it's still _hard_ to figure out the impacts of all these things, especially if you're a growing startup.