Workload Rightsizing And Capacity Optimization — AWS Solutions Architect (SAA-C03)
Utilization data always precedes purchase commitment decisions
Scenarios using "over-provisioned," "underutilized," or "inconsistent load" signal a rightsizing problem. The exam expects you to identify Compute Optimizer and Cost Explorer as diagnostic tools, not just cost dashboards. Candidates select Reserved Instances as the cost optimization answer without verifying that rightsizing the instance type is the prerequisite step. Reserving a too-large instance at a discount is still waste. The correct sequence: measure actual utilization, right-size the instance type, then apply the appropriate purchase commitment.
What This Pattern Tests
The exam presents an over-provisioned or under-provisioned workload and tests whether you identify the rightsizing opportunity. AWS Compute Optimizer analyzes CPU, memory, and network metrics to recommend instance type changes. CloudWatch metrics show utilization history. The trap is recommending Reserved Instances for an over-provisioned instance — you save 40% on a $200/month instance ($80 savings) when rightsizing first saves 75% ($150 savings) and then you reserve the smaller instance. Always rightsize before applying pricing optimizations.
Decision Axis
Current utilization vs. provisioned capacity. Rightsize first (reduce waste), then optimize pricing (reduce rate).
Associated Traps
More Top Traps on This Exam
Decision Rules
Select the instance family that matches the primary resource bottleneck type (compute-optimized C-family, not balanced M-family) AND the placement group type that minimizes inter-node network latency (cluster, not spread), treating these as two orthogonal axes that must both be satisfied.
Whether the stated IOPS and throughput values fall within gp3's independently provisionable ceiling (≤16,000 IOPS, ≤1,000 MiB/s), making gp3 the cost-optimal choice over io2 despite the database workload context.
When a fixed, over-provisioned fleet shows chronically low average CPU and traffic is variable rather than schedule-predictable, the correct two-lever action is Compute Optimizer for instance-type rightsizing plus a Target Tracking scaling policy to maintain a CPU target dynamically — Scheduled Scaling is disqualified because it requires a fixed, repeatable traffic schedule that the scenario cannot confirm.
Domain Coverage
Difficulty Breakdown