Oversized instances within Auto Scaling Groups lead to inflated baseline costs, even when scaling adjusts the number of instances dynamically. When workloads consistently use only a fraction of the available CPU, memory, or network capacity, there is an opportunity to downsize to smaller, less expensive instance types without sacrificing performance. Right-sizing helps balance capacity and efficiency, reducing compute spend while preserving workload stability.

Detection:

• Identify Auto Scaling Groups where instances exhibit low average CPU, memory, or network utilization relative to their capacity.
• Review instance sizing in relation to historical workload peaks and scaling behavior.
• Assess whether smaller, more cost-effective instance types could support the same workload with acceptable performance.
• Evaluate launch configurations or templates to determine if default instance types were selected without performance optimization.
• Confirm with application and infrastructure owners that resizing aligns with performance, availability, and SLA requirements.

This inefficiency occurs when an EC2 instance remains in a running state but is not actively utilized. These instances may be remnants of past projects, forgotten development environments, or temporarily created for testing and never decommissioned. If an instance shows consistently low or no CPU, network, or disk activity—and no active connections—it likely serves no operational purpose but continues to generate ongoing compute and storage charges.

Workloads are sometimes deployed in specific AWS regions based on legacy decisions, developer convenience, or perceived performance requirements. However, regional EC2 pricing can vary significantly, and placing instances in a suboptimal region can lead to higher compute costs, increased data transfer charges, or both. In particular, workloads that frequently communicate with resources in other regions—or that serve a user base concentrated elsewhere—can incur unnecessary costs. Re-evaluating regional placement can reduce these costs without compromising performance or availability when done strategically.

EC2 instances are often overprovisioned based on rough estimates, legacy patterns, or performance buffer assumptions. If an instance consistently uses only a small fraction of its provisioned CPU or memory, it likely represents an opportunity for rightsizing. These inefficiencies persist unless usage is periodically reviewed and instance types are adjusted to align with actual workload requirements.