A production database runs 24/7 on an r6i.4xlarge EC2 instance, and the team is confident the workload will run for at least three years. Which purchasing option provides the maximum cost savings?
Show answer and explanation
Answer: C
For a single fixed instance running around the clock with a fully predictable three-year lifetime, a three-year All Upfront Reserved Instance locks in the deepest available discount for that r6i usage and eliminates recurring hourly charges. The certainty of the workload means the long commitment carries no real risk of waste.
Why the other options are wrong
- A. On-Demand is the highest rate and suits unpredictable or short-lived workloads; using it for a three-year steady load simply maximizes spend.
- B. Spot capacity can be reclaimed with only two minutes of notice, which is unacceptable for a stateful production database.
- D. A one-year Compute Savings Plan is shallower on both tenure and discount depth than a three-year reservation on a known, fixed workload, even though it is more flexible.
Exam tip. Discount depth: 3-yr All Upfront > 3-yr Partial/No Upfront > 1-yr equivalents; commit long only when the workload is stable.