Which item is NOT listed as a common rightsizing mistake?

• A. Not addressing your resource shape
• B. Relying on recommendations that don't account for spikes in utilization
• C. Failing to rightsize beyond compute
• D. Overestimating the impact of reserved instances

Answer: (D)

Rightsizing aims to match each workload’s actual needs with the right resource levels. The common pitfalls you’d encounter while doing this revolve around not fully understanding the shape of the workload and its variability. If you don’t address resource shape, you might pick a size that works for average usage but misses memory or I/O needs, leading to under- or over-provisioning. If you rely on recommendations that don’t reflect spikes in utilization, you’ll miss peak demand and either pay for unused headroom or suffer performance during load. And if you only optimize compute, you neglect other dimensions like storage performance, network throughput, or database connections, so the overall fit isn’t truly right.

Overestimating the impact of reserved instances isn’t typically a rightsizing mistake because reserved instances pertain to long-term cost commitments and capacity planning, not the act of sizing resources to fit actual workloads. It’s more about cost optimization strategy after you’ve correctly sized the resources.