infra-cost-builder

name: infra-cost-builder description: End-to-end skill for creating infrastructure cost estimation and planning documents. Produces versioned Markdown documents with compute, storage, networking, third-party service, and operational cost breakdowns across deployment phases. Includes platform recommendations, scaling cost projections, monitoring strategy, and total cost of ownership analysis. Supports cross-agent review for cost accuracy and architectural feasibility. tools-needed: file read/write, shell execution, user interaction

Infrastructure Cost Builder Skill

Foundation: This skill inherits the quality framework from skills/builders/builder-foundation/SKILL.md. All Mid-Draft Quality Checks, Quality Dimensions, and Review Tiers defined there apply here. Below are enterprise-infra-specific quality prompts.

Purpose

Create a detailed infrastructure cost estimation and planning document from a Technical Architecture document (produced by tech-arch-builder) or equivalent system design. Output is a single versioned Markdown file that serves as the definitive reference for what infrastructure costs to expect, which platforms to use, and how costs scale with growth.

When To Use

• User asks to create an infrastructure cost estimate, deployment budget, or cloud cost analysis
• A Technical Architecture document exists or user provides equivalent system design context
• The system has multiple components that need infrastructure costing (compute, storage, networking, third-party services)
• Cost projections are needed across different growth phases or user tiers

Output Format

File: <slug>-infra-cost-v<N>.md

Where <slug> is a lowercase-hyphenated short name for the system (e.g., metalegends-infra-cost-v1.md).

Document Template

# <System Name> - Infrastructure Cost Estimation (v<N>)

> **Author:** <name>
> **Date:** <date>
> **Version:** v<N>
> **Status:** Draft | In Review | Approved

---

## Table of Contents

<Numbered list of all sections - auto-generate after writing>

## 1. Executive Summary

<2-3 paragraphs: total estimated monthly cost at launch, at scale, key cost drivers, and recommended platform strategy. A decision-maker should read this section alone and understand whether the infrastructure budget is reasonable for the product scope.>

## 2. Infrastructure Overview

### 2.1 Architecture Cost Map

<Mermaid diagram showing all infrastructure components with estimated monthly costs annotated on each node. Use graph TD or graph LR. Each node label should include the component name and cost range.>

### 2.2 Cost Assumptions

<List all assumptions: expected user counts per phase, requests per second, storage growth rate, geographic deployment, pricing tier (on-demand vs reserved), currency.>

### 2.3 Pricing Model

<Explain the pricing approach: on-demand vs reserved instances, spot instances for non-critical workloads, commitment discounts, free tier usage where applicable. State the pricing date - cloud prices change frequently.>

## 3. Compute Costs

### 3.1 Application Servers

| Component | Instance Type | vCPUs | RAM | Count | Monthly Cost | Scaling Trigger |
|-----------|--------------|-------|-----|-------|-------------|----------------|
| <component> | <type> | <vcpus> | <ram> | <count> | <cost> | <trigger> |

### 3.2 Background Workers & Job Processors

| Worker Type | Instance Type | Count | Monthly Cost | Purpose |
|-------------|--------------|-------|-------------|---------|
| <worker> | <type> | <count> | <cost> | <purpose> |

### 3.3 Compute Scaling Projections

| Phase | Users | Compute Instances | Monthly Compute Cost |
|-------|-------|-------------------|---------------------|
| Launch | <users> | <instances> | <cost> |
| Growth | <users> | <instances> | <cost> |
| Scale | <users> | <instances> | <cost> |

## 4. Database & Storage Costs

### 4.1 Primary Database

| Parameter | Value | Monthly Cost |
|-----------|-------|-------------|
| Engine | <engine> | - |
| Instance type | <type> | <cost> |
| Storage (GB) | <size> | <cost> |
| IOPS | <iops> | <cost> |
| Read replicas | <count> | <cost> |
| Backups | <retention> | <cost> |
| **Subtotal** | | **<total>** |

### 4.2 Cache Layer

| Parameter | Value | Monthly Cost |
|-----------|-------|-------------|
| Engine | <engine> | - |
| Instance type | <type> | <cost> |
| Node count | <count> | <cost> |
| **Subtotal** | | **<total>** |

### 4.3 Object Storage & CDN

| Storage Type | Estimated Size | Monthly Cost | Purpose |
|-------------|---------------|-------------|---------|
| <type> | <size> | <cost> | <purpose> |

### 4.4 Storage Scaling Projections

| Phase | Database Size | Cache Size | Object Storage | Monthly Storage Cost |
|-------|-------------|-----------|---------------|---------------------|
| Launch | <size> | <size> | <size> | <cost> |
| Growth | <size> | <size> | <size> | <cost> |
| Scale | <size> | <size> | <size> | <cost> |

## 5. Networking Costs

### 5.1 Data Transfer

| Transfer Type | Estimated Volume | Monthly Cost |
|--------------|-----------------|-------------|
| Ingress | <volume> | <cost> |
| Egress | <volume> | <cost> |
| Inter-region | <volume> | <cost> |
| CDN bandwidth | <volume> | <cost> |
| **Subtotal** | | **<total>** |

### 5.2 Load Balancing

| Load Balancer | Type | Monthly Cost |
|--------------|------|-------------|
| <lb> | <type> | <cost> |

### 5.3 DNS & Domain

| Service | Monthly Cost |
|---------|-------------|
| <service> | <cost> |

## 6. Third-Party Services

### 6.1 Service Cost Breakdown

| Service | Purpose | Tier/Plan | Monthly Cost | Annual Cost | Lock-in Risk |
|---------|---------|-----------|-------------|-------------|-------------|
| <service> | <purpose> | <tier> | <cost> | <cost> | <risk> |

### 6.2 Third-Party Alternatives

For each significant third-party cost, document at least one alternative:

| Primary Service | Monthly Cost | Alternative | Alt Monthly Cost | Migration Effort |
|----------------|-------------|-------------|-----------------|-----------------|
| <service> | <cost> | <alt> | <cost> | <effort> |

## 7. Blockchain & Web3 Costs (if applicable)

### 7.1 Smart Contract Deployment

| Contract | Deployment Gas | Estimated Cost | Frequency |
|----------|--------------|---------------|-----------|
| <contract> | <gas> | <cost> | <frequency> |

### 7.2 Transaction Costs

| Transaction Type | Gas per Tx | Estimated Monthly Volume | Monthly Cost |
|-----------------|-----------|------------------------|-------------|
| <type> | <gas> | <volume> | <cost> |

### 7.3 Decentralized Storage

| Storage Service | Monthly Volume | Monthly Cost |
|----------------|---------------|-------------|
| <service> | <volume> | <cost> |

## 8. Monitoring, Logging & Observability

### 8.1 Monitoring Stack

| Tool | Purpose | Tier | Monthly Cost |
|------|---------|------|-------------|
| <tool> | <purpose> | <tier> | <cost> |

### 8.2 Log Management

| Parameter | Value | Monthly Cost |
|-----------|-------|-------------|
| Log volume (GB/day) | <volume> | - |
| Retention period | <days> | - |
| Log service | <service> | <cost> |

### 8.3 Alerting & Incident Management

| Service | Purpose | Monthly Cost |
|---------|---------|-------------|
| <service> | <purpose> | <cost> |

## 9. CI/CD & Development Infrastructure

### 9.1 Build & Deploy Pipeline

| Service | Purpose | Tier | Monthly Cost |
|---------|---------|------|-------------|
| <service> | <purpose> | <tier> | <cost> |

### 9.2 Development & Staging Environments

| Environment | Infrastructure | Monthly Cost |
|-------------|---------------|-------------|
| <env> | <infra summary> | <cost> |

## 10. Security Infrastructure

| Service | Purpose | Monthly Cost |
|---------|---------|-------------|
| <service> | <purpose> | <cost> |

## 11. Platform Recommendations

### 11.1 Primary Platform Recommendation

<Recommended cloud provider or platform mix with rationale. Include 2-3 alternatives considered and why they were not selected.>

### 11.2 Platform Comparison

| Factor | <Platform A> | <Platform B> | <Platform C> |
|--------|-------------|-------------|-------------|
| Compute pricing | <comparison> | <comparison> | <comparison> |
| Database options | <comparison> | <comparison> | <comparison> |
| Global reach | <comparison> | <comparison> | <comparison> |
| Free tier | <comparison> | <comparison> | <comparison> |
| Managed services | <comparison> | <comparison> | <comparison> |
| Blockchain support | <comparison> | <comparison> | <comparison> |
| Developer experience | <comparison> | <comparison> | <comparison> |
| **Best for** | <summary> | <summary> | <summary> |

### 11.3 Multi-Cloud Strategy (if applicable)

<When and why to use multiple providers. Which components go where.>

## 12. Total Cost of Ownership

### 12.1 Monthly Cost Summary by Category

| Category | Launch | Growth | Scale |
|----------|--------|--------|-------|
| Compute | <cost> | <cost> | <cost> |
| Database & Storage | <cost> | <cost> | <cost> |
| Networking | <cost> | <cost> | <cost> |
| Third-Party Services | <cost> | <cost> | <cost> |
| Blockchain/Web3 | <cost> | <cost> | <cost> |
| Monitoring & Observability | <cost> | <cost> | <cost> |
| CI/CD & Dev Infrastructure | <cost> | <cost> | <cost> |
| Security | <cost> | <cost> | <cost> |
| **Monthly Total** | **<total>** | **<total>** | **<total>** |
| **Annual Total** | **<total>** | **<total>** | **<total>** |

### 12.2 Cost Per User

| Phase | MAU | Monthly Infra Cost | Cost Per MAU |
|-------|-----|-------------------|-------------|
| Launch | <mau> | <cost> | <cost/mau> |
| Growth | <mau> | <cost> | <cost/mau> |
| Scale | <mau> | <cost> | <cost/mau> |

### 12.3 Cost Scaling Curve

<Mermaid diagram (xychart-beta or graph) showing how total monthly cost scales with user count. Identify the cost inflection points where infrastructure needs step up.>

### 12.4 Cost Optimization Opportunities

| Optimization | Savings Estimate | Effort | When to Apply |
|-------------|-----------------|--------|--------------|
| <optimization> | <savings> | <effort> | <timing> |

## 13. Risks & Cost Uncertainties

| Risk | Impact on Cost | Likelihood | Mitigation |
|------|---------------|------------|------------|
| <risk> | <impact> | <likelihood> | <mitigation> |

### 13.1 Honest Assessment

<Acknowledge cost uncertainties directly. What numbers are estimates vs. quotes? Where could costs be 2-5x higher than projected? What usage patterns could break the budget model?>

## 14. References

| Source | URL |
|--------|-----|
| <source> | <url> |

Mermaid Diagram Requirements

Infrastructure cost documents should include 3-6 Mermaid diagrams.

Required Diagrams

1. Architecture cost map (graph TD/LR) - all components with cost annotations
2. Cost scaling curve (xychart-beta or graph) - total cost vs. user growth
3. Monthly cost breakdown (pie or graph) - visual split by category

Optional Diagrams

• Per-phase infrastructure topology showing scaling
• Data flow with bandwidth annotations
• CI/CD pipeline with cost per stage

Style Rules

• Use cost labels on nodes and edges where they clarify the budget
• Never use \n or <br/> for line breaks in Mermaid node labels - neither renders reliably across Mermaid environments (Notion cuts off multi-line text, \n is ignored everywhere). Keep all node labels on a single line.
• No emojis in diagrams
• Place each diagram immediately after the paragraph introducing the concept

Writing Rules

1. All costs are monthly unless stated otherwise. Annual costs are shown as 12x monthly. One-time costs (deployment, setup) are labeled clearly.

2. Use current pricing. State the pricing date and source. Cloud pricing changes frequently - note when estimates may be stale. Link to pricing calculators where available.

3. Show the math. Every cost estimate should be traceable: instance type x count x hours = cost. Do not use round numbers without showing what produces them.

4. Phase-aligned costs. Map infrastructure costs to the product's development phases. Launch costs are different from scale costs - show both.

5. Alternatives for every major cost. Every service costing $100+/month should have at least one alternative documented with migration effort estimate.

6. Cost per user is mandatory. Calculate cost-per-MAU at each phase. This is the single most important metric for evaluating infrastructure efficiency.

7. Honest assessment is mandatory. The Risks section must acknowledge where estimates are uncertain, what could be 2-5x more expensive, and what assumptions could prove wrong.

8. No marketing language. This is a financial planning document. Facts and numbers over adjectives. "Cost-effective" is not a number.

9. Reserved vs on-demand. Show both pricing models where significant savings exist (typically compute and database). Recommend when to commit to reserved pricing based on usage stability.

10. Include hidden costs. Data transfer, DNS queries, API calls, support plans, SSL certificates - these add up. Do not omit them because they seem small individually.

Mid-Draft Quality Check

Enterprise-Infra-Specific Quality Prompts

Sprint contract pattern recommended for enterprise infra docs (typically 500+ lines). See builder-foundation for details.

Document evaluator recommended for enterprise infra docs. See builder-foundation for invocation pattern.

Cross-Agent Deliverable Review

After drafting, optionally run cross-agent review.

Critic Roles

Gemini - Cost Logic & Feasibility

Review the following infrastructure cost estimation document for logical consistency and feasibility.

Verify:
1. Cost calculations are arithmetically correct
2. Instance sizing matches the stated workload (not over or under provisioned)
3. Scaling projections are realistic for the stated user growth
4. No major cost categories are missing
5. Third-party service estimates match their actual pricing tiers
6. Networking costs account for realistic data transfer patterns
7. The total cost is feasible for the project's stage and funding
8. Cost per user is realistic compared to industry benchmarks
9. Reserved vs on-demand recommendations are appropriate
10. Cost risks and uncertainties are honestly assessed

Output format:
1) CRITICAL_ISSUES (missing costs, arithmetic errors, infeasible estimates)
2) COST_GAPS (underestimated categories, missing line items)
3) FEASIBILITY_CONCERNS (budget vs scope mismatch, scaling cliff costs)
4) OPTIMIZATION_OPPORTUNITIES (missed savings, better pricing models)
5) READY_FOR_BUDGETING (yes/no + reason)

Claude - Architecture & Platform Alignment

Review the following infrastructure cost estimation document for architectural alignment and platform suitability.

Verify:
1. Infrastructure choices match the technical architecture requirements
2. Platform recommendations are well-reasoned with genuine alternatives
3. Monitoring and observability stack is adequate for the system complexity
4. CI/CD infrastructure supports the deployment strategy
5. Security infrastructure is sufficient for the threat model
6. Database and cache sizing matches the data model requirements
7. The infrastructure scales gracefully without cost cliffs
8. Vendor lock-in risks are identified and migration paths exist
9. Development and staging environments are realistic
10. The document is detailed enough for procurement without ambiguity

Output format:
1) ARCHITECTURE_MISMATCHES (infra that doesn't match the tech arch)
2) PLATFORM_ISSUES (poor platform choices, missing evaluations)
3) COMPLETENESS_GAPS (missing sections, insufficient detail)
4) SCALABILITY_ASSESSMENT (will costs scale linearly or exponentially?)
5) READY_FOR_BUDGETING (yes/no + reason)

Review Procedure

1. Concatenate infrastructure cost document content into inline prompts (never reference file paths)
2. Run critics in parallel with per-agent timeouts (Codex=480s, Claude/Gemini=180s)
3. Merge feedback, prioritizing consensus items and all CRITICAL_ISSUES
4. Apply accepted changes and increment version
5. Max 2 rounds for deliverable review

Versioning

• v1: First draft from Technical Architecture document
• v2: After user feedback or cross-agent review
• v3: Final version

Only keep the latest version. Delete previous versions when a new one is created.

Review Checklist

Before finalizing, verify items in priority order per builder-foundation tiers.

Critical Items (Claude Weak Spots)

• Cost calculations are traceable: instance type x count x hours = cost (not round numbers)
• Hidden costs included: egress, API calls, support plans, DNS queries, SSL certs
• Platform recommendation genuinely compares 2-3 alternatives with specific trade-offs
• Honest assessment acknowledges where estimates could be 2-5x higher than projected
• Cost optimization opportunities are specific to this system (not generic advice)
• Scaling projections identify cost cliffs where infrastructure needs step up

Standard Items (Claude Strong Spots)

• All tech-arch components costed; compute/storage sizing matches workload
• Networking costs include transfer, CDN, load balancing; third-party services costed
• Cost per user at each phase; 3+ user tiers; monthly and annual projections
• Pricing sources and dates documented; 3+ diagrams; no placeholder text

Output Rules

• Never write files larger than 200 lines in a single response
• For large files, write in sequential chunks and continue automatically
• If you hit an output token limit, resume exactly where you stopped

Version: 2.0.0