Cost Calculations

Overview

FinFocus supports two primary workflows for analyzing infrastructure costs: Projected Costs (pre-deployment) and Actual Costs (post-deployment).

1. Projected Costs (Pre-Deployment)

The projected cost workflow estimates monthly spending based on the resources defined in your Pulumi plan, before they are created in the cloud.

Projected Workflow

1. Parse Plan: FinFocus reads the JSON output from pulumi preview --json.
2. Map Resources: It identifies cloud resources (e.g., aws:ec2/instance) and extracts relevant properties (Type, Region, Size).
3. Route to Plugin: The system routes the resource data to the appropriate plugin (e.g., aws-public).
4. Lookup Pricing: The plugin queries its pricing database (usually public list prices) to find a match.
5. Calculate: Monthly costs are calculated assuming 730 hours/month of usage (on-demand rates).
6. Report: The Core engine aggregates these estimates into a summary table.

Projected Use Cases

• Budget approval before deployment.
• Comparing costs between different instance types or regions.
• CI/CD checks to prevent cost spikes.

2. Actual Costs (Post-Deployment)

The actual cost workflow retrieves historical spending data for resources that have already been deployed and are running.

Actual Workflow

1. Parse Plan: FinFocus parses the Pulumi plan to identify the specific resource IDs (e.g., i-0123456789abcdef0) of deployed resources.
2. Route to Plugin: The request is routed to a production-grade plugin (e.g., aws-costexplorer).
3. Query Provider API: The plugin uses the cloud provider’s API to fetch billing data for those specific resource IDs over a specified time range.
4. Return Data: The plugin returns the exact spend, including taxes, credits, and discounts (RIs/Savings Plans).
5. Report: The Core engine presents the historical spend data.

Actual Use Cases

• Chargeback/showback reports.
• Validating that reserved instances are being applied.
• Monitoring daily spend trends.

Key Differences

Feature	Projected Costs	Actual Costs
Timing	Before Deployment	After Deployment
Data Source	Public List Prices (MSRP)	Billing API (Real Invoices)
Accuracy	Estimate	Precise
Auth	Usually None	Required (API Keys)
Plugin	aws-public	aws-costexplorer

Related Documentation

For more details on the plugins referenced above (aws-public, aws-costexplorer) and related topics:

• Plugin ecosystem — Overview of FinFocus plugin architecture
• Compatibility matrix — Compare plugin capabilities
• Troubleshooting — Common issues and solutions
• E2E tests — End-to-end testing with real cloud resources