AWS Cost Explorer: Custom Reports That Drive Savings

Beyond the Default Dashboard

AWS Cost Explorer is the starting point for any cost optimization effort, but most teams only use the default view. Custom reports and anomaly detection turn Cost Explorer into a proactive cost governance tool that catches overruns before they hit your invoice.

Essential Custom Reports

1. Daily Cost Trend by Service

Create a daily granularity report grouped by Service. Set the time range to the last 30 days. This view instantly highlights cost spikes and identifies which service caused them.

2. Cost by Tag (Team/Environment)

Group costs by your cost allocation tags (e.g., Environment, Team, Project). This report is essential for chargeback and showback models. It answers: "Which team is spending the most?" and "Are dev environments costing more than production?"

3. Untagged Resources Report

Filter by tag where Environment = (not tagged). This shows your tagging gaps — resources that aren't being tracked in your cost allocation model.

4. Month-over-Month Comparison

Compare the current month against the previous month at daily granularity. Look for divergence patterns — if costs are consistently higher each day, something has changed in your infrastructure.

Setting Up Anomaly Detection

AWS Cost Anomaly Detection uses machine learning to identify unusual spending patterns. Configure it to:

1. Create a monitor for each AWS account or cost allocation tag
2. Set alert thresholds (e.g., notify when anomaly exceeds $50/day)
3. Route alerts to SNS → email, Slack, or PagerDuty

aws ce create-anomaly-monitor \
  --anomaly-monitor '{
    "MonitorName": "production-cost-monitor",
    "MonitorType": "DIMENSIONAL",
    "MonitorDimension": "SERVICE"
  }'

Automating Weekly Reports

Use the Cost Explorer API to generate weekly cost summaries and email them to stakeholders:

1. Create a Lambda function that calls get-cost-and-usage
2. Format the results as an HTML table
3. Send via SES to the finance and engineering teams
4. Schedule with EventBridge to run every Monday at 9 AM

Eazy SaaS Tip: Save your custom reports as bookmarks in Cost Explorer. Share the URL with your team — it encodes all filters and groupings, so everyone sees the same view.