Which of the following is a common error when purchasing RIs and CUDs?

• A. Delaying purchasing RIs too long
• B. Purchasing at the right time
• C. Buying the right RIs or CUDs
• D. Not managing them after purchase

Answer: (A)

The key idea here is that Reserved Instances and Committed Use Discounts reward you for committing to future usage with a discount. The most common mistake is delaying the purchase. If you wait, you continue paying standard on-demand rates for the workloads you’re running, so you miss out on the discounted prices for the period you could have covered. The longer you wait, the more you pay in real terms, and you may also miss aligning the discount with your actual steady workloads. Buying at the right time, selecting the appropriate RIs or CUDs, and then actively managing them after purchase are the correct practices; delaying the purchase is the pitfall highlighted by the question.