Technical Specification Template Generator

# Technical Specification: Usage-based billing dashboard

## 1. Summary
Spec type: Feature
Complexity: Medium - Several owners, at least one integration point, and staged validation.
Audience: Engineering, product, design, support, and finance stakeholders

Customers need a clear way to inspect usage, forecast spend, and understand billing changes before invoices are generated.

## 2. Goals
- Show current usage by workspace and billing period
- Estimate projected invoice total from current usage pace
- Flag usage anomalies before billing closes

## 3. Non-goals
- Replace the existing invoicing provider
- Support custom enterprise contract rules in the first release

## 4. Requirements
- Authenticated admins can view usage by day, product area, and workspace
- Users can export the current period usage summary as CSV
- System records audit events when billing data is viewed or exported

## 5. Proposed architecture
Add a billing usage read model populated from metering events. Serve dashboard data through a cached API route with tenant-scoped authorization checks.

## 6. Interfaces and integrations
- GET /api/billing/usage?period=current returns daily usage totals
- GET /api/billing/usage/export streams a CSV export
- Metering event consumer writes normalized usage rows

## 7. Data model
- BillingUsageDaily: workspaceId, productArea, usageDate, quantity, unit, sourceEventCount
- BillingUsageExport: workspaceId, requestedById, periodStart, periodEnd, fileKey

## 8. Security, privacy, and permissions
- Define who can access this workflow and which roles are blocked.
- Confirm tenant isolation, audit logging, and sensitive-field handling.
- Note secrets, external credentials, or provider scopes required for deployment.

## 9. Observability and operations
- Metrics: latency, error rate, queue lag, volume, and conversion or usage indicators.
- Logs: include request ids, tenant ids, owner ids, and provider response codes where safe.
- Alerts: define thresholds, escalation owner, and runbook link.

## 10. Rollout plan
- Build behind a feature flag or internal-only gate.
- Ship to staging with seeded or anonymized production-like data.
- Release to a small cohort, verify metrics, then expand.
- Document rollback steps and data cleanup needs.

## 11. Acceptance criteria
- Dashboard loads current period usage in under 1.5 seconds for workspaces with 90 days of data
- CSV export includes the same totals shown in the dashboard
- Non-admin users receive a 403 for all billing usage endpoints

## 12. Risks and mitigations
- Metering events may arrive late or out of order
- Projected invoice totals can be misunderstood as final charges
- Large workspaces may require aggregation before API reads

## 13. Open questions
- Which decision must be made before implementation starts?
- Which dependency could change scope or timing?
- What evidence will reviewers use to approve this design?