When building Guardian Pro's cost intelligence module, we made a deliberate architectural decision: use AWS Cost and Usage Reports (CUR) as the primary data source instead of the Cost Explorer API. Here is why.

The Cost Explorer Limitation

The AWS Cost Explorer API is the most common starting point for cost analysis tools. It is convenient -- a few API calls and you have cost data. But it comes with significant limitations:

Aggregated data only: Cost Explorer returns pre-aggregated data. You cannot drill down to individual resource costs without significant filtering gymnastics.
API rate limits: The Cost Explorer API has strict throttling (5 requests per second). At scale, this becomes a bottleneck.
Limited granularity: Daily or monthly granularity only. No hourly breakdowns without CloudWatch integration.
14-month retention: Historical data beyond 14 months requires separate archival.
Cost: Each Cost Explorer API request costs $0.01. For a platform scanning multiple accounts continuously, this adds up.

The CUR Advantage

Cost and Usage Reports deliver line-item billing data that Guardian Pro ingests and indexes automatically for fast, per-resource queries.

Resource-Level Granularity

CUR data includes individual resource IDs, usage types, and pricing details. When Guardian Pro tells you an EC2 instance costs a specific amount per day, that figure comes from actual billing line items, not estimates.

Correlation with Security Findings

Because we have resource-level cost data, Guardian Pro can answer questions like: "How much are we spending on resources with critical security findings?" This is the foundation of our cost exposure analysis.

No API Rate Limits

CUR files are delivered to S3 on a schedule. Guardian Pro's sync process ingests them without competing for API rate limits. This means consistent performance regardless of how many accounts you monitor.

Full Historical Data

CUR data persists in S3 indefinitely (subject to your retention policies). Guardian Pro maintains daily cost records, enabling long-term trend analysis and forecasting.

How Guardian Pro Processes CUR Data

Guardian Pro processes your CUR data automatically, generating per-resource cost breakdowns, savings recommendations, budget evaluations, and anomaly detection. The entire process completes without manual intervention, and results are pushed to your dashboard in real time.

Anomaly Detection

Guardian Pro uses multiple complementary detection methods to catch different types of spending irregularities — from gradual cost creep and sudden spending spikes to service-specific anomalies and unexpected new services appearing in your billing. Each method analyses your spending from a different angle, ensuring comprehensive anomaly coverage.

The Trade-Off

CUR-based analysis requires initial setup: you need to configure a Cost and Usage Report in your AWS account and wait for the first delivery (up to 24 hours). Guardian Pro's onboarding wizard guides you through this process, and our CUR status monitoring shows you exactly where you are in the setup flow.

The setup investment pays for itself immediately. The depth and accuracy of CUR-based analysis is in a different league from Cost Explorer API responses.

Conclusion

If you are evaluating cost management tools, ask what data source they use. Cost Explorer is fine for a quick dashboard glance, but for production cost governance -- anomaly detection, resource-level attribution, security-cost correlation -- CUR is the only serious option.

Guardian Pro's cost intelligence is built on this foundation from the ground up. Start your free trial to see the difference.

Why CUR-Based Cost Analysis Beats Cost Explorer