☁︎SAA-C03

Cost Optimization

Cost & Billing — Concept (Budgets, Cost Explorer, Trusted Advisor, Compute Optimizer, Savings Plans)

Why this group

Cost optimization is one of the 6 Well-Architected pillars and ~20 % of the SAA-C03 domain weighting. You need to recognize the right tool for "see, plan, predict, optimize".

AWS Cost Explorer

  • Visualize & analyze historical and forecast cost / usage.
  • Group by service, account, tag, region, usage type, …
  • Daily / monthly granularity (recent 12 months free).
  • RI / Savings Plan recommendations.
  • Hourly granularity at extra cost.

AWS Budgets

  • Set monthly cost / usage / RI utilization / Savings Plan coverage budgets.
  • Alerts via SNS when forecast / actual exceeds thresholds.
  • Can trigger Budget Actions (e.g. stop EC2, apply SCP) via Lambda or directly.
  • 2 budgets free per account.

AWS Cost & Usage Report (CUR)

  • Most detailed billing data, line-item, Parquet-compatible.
  • Drops to S3; analyze with Athena / Redshift / QuickSight.

AWS Pricing Calculator

  • Pre-purchase cost estimates per service.

Trusted Advisor

  • Best-practice checks across cost, performance, security, fault tolerance, service limits.
  • Free tier = limited checks.
  • Business / Enterprise Support unlocks all checks + programmatic access.

AWS Compute Optimizer

  • ML-based recommendations to right-size:
    • EC2 instances
    • ASGs
    • EBS volumes
    • Lambda functions
  • Analyzes CloudWatch metrics + historical usage; suggests cheaper / better-fit types.

Savings Plans & Reserved Instances (recap)

  • Compute Savings Plan = flexible commitment ($/hr) across EC2 + Lambda + Fargate, any region/family — up to ~66 % off.
  • EC2 Instance Savings Plan = locked to a family + region — up to ~72 % off, less flexible.
  • Reserved Instances (RI):
    • Standard RI = lowest cost, locked to instance family.
    • Convertible RI = can exchange to similar family — smaller discount.
  • Spot = up to 90 % off, can be interrupted.
  • 1- or 3-year terms; all-/partial-/no-upfront.

Other levers

  • S3 lifecycle policies (move to IA/Glacier).
  • EBS gp3 over gp2 (cheaper + decoupled IOPS).
  • VPC Endpoints for S3/DynamoDB to avoid NAT data charges.
  • Auto Scaling + Spot.
  • Right-sizing with Compute Optimizer.
  • Reserved capacity for RDS, Redshift, ElastiCache, OpenSearch, DynamoDB.

AWS Organizations cost features

  • Consolidated billing — single payer, volume discounts across accounts.
  • Cost Allocation Tags — tag-based grouping in CE/CUR.
  • Billing alerts via Budgets.

Common exam scenarios

  1. "Forecast next month's spend and group by service" → Cost Explorer.
  2. "Stop EC2 instances when monthly spend exceeds $X" → AWS Budgets + Budget Action.
  3. "Right-size EC2 fleet" → Compute Optimizer.
  4. "Get programmatic security best practice checks" → Trusted Advisor with Business/Enterprise Support.
  5. "Lowest TCO for known 24×7 prod workload" → Reserved Instance or Savings Plan.
  6. "Save cost on rarely-accessed S3 data" → S3 lifecycle → IA / Glacier.
  7. "Avoid NAT charges from private subnet S3 calls" → S3 Gateway endpoint.

Exam tip

  • See / analyze = Cost Explorer.
  • Limit / alert = Budgets.
  • Right-size = Compute Optimizer.
  • Best-practice checks = Trusted Advisor.
  • Cheapest steady compute = Savings Plans / RIs (Spot if interruptible).

References