AWS Rightsizing: EC2, Graviton, gp3, RDS and Lambda Memory

On AWS, “rightsizing” is several different moves: a smaller instance in the same family, the same size on newer or ARM-based hardware, a cheaper volume type, fewer provisioned IOPS, or less memory on a function. ZopNight has a rule for each, and every one of them must name the target and read both the source and target rates before it will show a saving.

EC2

• EC2 Rightsizing reads 30-day average CPU. Under 2% it proposes a two-step same-family downsize, between 2% and 5% a one-step downsize, and above 5% it stays silent. A memory veto blocks the move when the smaller size would run out of memory.
• Graviton Migration Opportunity names the shape-preserving ARM equivalent, skipping Windows, instances already on arm64, and self-managed databases or brokers.
• EC2 Older Instance Family proposes the same size on the current generation, for example m5 to m6i, when CPU is low.
• GPU Instance Low Utilization needs the NVIDIA GPU utilization series from the CloudWatch agent, at least 7 days of history, and a provably smaller GPU size in the same family.

Storage

• EBS gp2 to gp3 Migration compares the two per-GB rates and nets out any IOPS or throughput charge the volume would inherit on gp3.
• EBS Provisioned IOPS Over-Allocation trims io1/io2 IOPS only when utilization data exists, and never on volumes named for standby, replica or backup roles.
• S3 Storage Tier Migration needs S3 request metrics showing a cold bucket before suggesting Standard-IA. The lifecycle and noncurrent-version rules abstain until per-bucket cold-byte data from S3 Storage Lens is available, rather than estimating.

Databases

• RDS Instance Right-sizing reads CPU and the FreeableMemory metric and prices only the instance-hours portion of the bill.
• RDS Non-Graviton Instance applies only to engines with a Graviton class.
• RDS Multi-AZ on Non-Production Instance fires on dev/test instances, never on anything tagged production.

Containers and serverless

• ECS Fargate Oversized Task requires low CPU and low peak memory before shrinking the task size.
• Lambda Over-Provisioned Memory fires when peak memory used is under half of configured memory, pricing only the GB-second portion of the function’s cost.

Applying

EC2 Rightsizing runs as a resize with a stop; EBS provisioned IOPS resize in place, and Lambda memory findings are advisory. A stop-requiring resize on a stateful resource is demoted to advisory. After a change, ZopNight checks the instance against the target it recommended and records whether the change was adopted. More on AWS EC2, AWS Lambda and AWS RDS; fact sheets for EC2 and EBS; full list in AWS recommendations.