Infrastructure Documenter Skill

Overview

This skill helps you create clear, maintainable infrastructure documentation. Covers architecture diagrams, runbooks, system documentation, operational procedures, and documentation-as-code practices.

Documentation Philosophy

Principles

1. Living documentation: Keep it in sync with reality
2. Audience-aware: Different docs for different readers
3. Actionable: Every doc should help someone do something
4. Version-controlled: Documentation changes tracked with code

Document Types

Type	Audience	Purpose
Architecture	Engineers	Understand system design
Runbooks	Ops/SRE	Handle incidents
API Docs	Developers	Integrate with system
Onboarding	New hires	Get up to speed
Decision Records	Future you	Understand why

Architecture Documentation

System Architecture Overview

# System Architecture

## Overview

[Project Name] is a [type] application that [purpose].

## High-Level Architecture

┌─────────────────────────────────────────────────────────────┐ │ Users │ └─────────────────────────────────────────────────────────────┘ │ ▼ ┌─────────────────────────────────────────────────────────────┐ │ Vercel Edge │ │ ┌─────────────────┐ ┌─────────────────┐ │ │ │ Next.js App │ │ Edge Functions │ │ │ └─────────────────┘ └─────────────────┘ │ └─────────────────────────────────────────────────────────────┘ │ ┌───────────────┼───────────────┐ ▼ ▼ ▼ ┌─────────────────┐ ┌─────────────────┐ ┌─────────────────┐ │ Supabase │ │ Redis │ │ Stripe │ │ - PostgreSQL │ │ - Session │ │ - Payments │ │ - Auth │ │ - Cache │ │ - Webhooks │ │ - Realtime │ │ │ │ │ │ - Storage │ │ │ │ │ └─────────────────┘ └─────────────────┘ └─────────────────┘

## Components

### Frontend (Next.js App)
- **Location**: Vercel Edge Network
- **Framework**: Next.js 14 (App Router)
- **Styling**: Tailwind CSS + shadcn/ui
- **State**: Zustand + React Query

### Backend Services
| Service | Provider | Purpose |
|---------|----------|---------|
| Database | Supabase | PostgreSQL with RLS |
| Auth | Supabase Auth | User authentication |
| Storage | Supabase Storage | File uploads |
| Cache | Upstash Redis | Session & API cache |
| Payments | Stripe | Subscriptions |
| Email | Resend | Transactional emails |

### Data Flow

1. User request → Vercel Edge
2. SSR/API Route processes request
3. Database queries via Supabase client
4. Response cached at edge (when applicable)
5. Response returned to user

## Security

### Authentication Flow
1. User signs in via Supabase Auth
2. JWT token issued and stored in cookie
3. Server validates token on each request
4. RLS policies enforce data access

### Data Protection
- All data encrypted at rest (AES-256)
- TLS 1.3 for data in transit
- Secrets stored in Vercel environment
- PII fields encrypted in database

Mermaid Diagrams

## Request Flow

```mermaid
sequenceDiagram
    participant U as User
    participant V as Vercel
    participant N as Next.js
    participant S as Supabase
    participant R as Redis

    U->>V: HTTPS Request
    V->>N: Route to App

    alt Cached Response
        N->>R: Check Cache
        R-->>N: Cache Hit
        N-->>U: Return Cached
    else Cache Miss
        N->>S: Query Database
        S-->>N: Data
        N->>R: Store in Cache
        N-->>U: Return Response
    end

Database Schema

erDiagram
    users ||--o{ projects : owns
    users {
        uuid id PK
        text email
        text name
        timestamp created_at
    }
    projects ||--o{ tasks : contains
    projects {
        uuid id PK
        uuid user_id FK
        text name
        text status
    }
    tasks {
        uuid id PK
        uuid project_id FK
        text title
        boolean completed
    }

## Runbooks

### Runbook Template

```markdown
# Runbook: [Service Name] - [Issue Type]

## Overview
Brief description of the issue and when this runbook applies.

## Severity
- **P1 (Critical)**: Complete outage
- **P2 (High)**: Degraded service
- **P3 (Medium)**: Minor impact
- **P4 (Low)**: No user impact

## Detection
How this issue is typically detected:
- [ ] Alert from [monitoring system]
- [ ] User report
- [ ] Automated check failure

## Impact Assessment
- **Users affected**: All / Segment / None
- **Data at risk**: Yes / No
- **Revenue impact**: High / Medium / Low / None

## Prerequisites
- [ ] Access to [system/dashboard]
- [ ] Credentials for [service]
- [ ] Contact info for [team/person]

## Resolution Steps

### Step 1: Verify the Issue
```bash
# Check service status
curl -I https://api.example.com/health

# Check logs
vercel logs --follow

Step 2: Identify Root Cause

Common causes:

• Database connection pool exhausted
• Memory limit reached
• External service down
• Bad deployment

Step 3: Apply Fix

If Database Issue:

# Check connection count
SELECT count(*) FROM pg_stat_activity;

# Kill idle connections
SELECT pg_terminate_backend(pid)
FROM pg_stat_activity
WHERE state = 'idle' AND query_start < now() - interval '1 hour';

If Bad Deployment:

# Rollback to previous deployment
vercel rollback

Step 4: Verify Fix

# Check service health
curl https://api.example.com/health

# Monitor error rates for 15 minutes

Escalation

If unable to resolve within 30 minutes:

1. Page on-call engineer: [contact]
2. Notify stakeholders in #incidents
3. Update status page

Post-Incident

• Create incident report
• Schedule post-mortem (P1/P2 only)
• Update this runbook if needed

Related Links

• Dashboard
• Logs
• Metrics

### Database Runbooks

```markdown
# Runbook: Database Performance Issues

## Symptoms
- Slow API responses (>1s)
- Timeout errors in logs
- High database CPU in dashboard

## Quick Checks

### 1. Check Active Connections
```sql
SELECT
  state,
  count(*),
  max(now() - query_start) as max_duration
FROM pg_stat_activity
GROUP BY state;

2. Find Long-Running Queries

SELECT
  pid,
  now() - query_start AS duration,
  query
FROM pg_stat_activity
WHERE state = 'active'
  AND now() - query_start > interval '30 seconds'
ORDER BY duration DESC;

3. Check Table Sizes

SELECT
  schemaname,
  tablename,
  pg_size_pretty(pg_total_relation_size(schemaname || '.' || tablename)) as size
FROM pg_tables
WHERE schemaname = 'public'
ORDER BY pg_total_relation_size(schemaname || '.' || tablename) DESC
LIMIT 10;

4. Check Missing Indexes

SELECT
  relname,
  seq_scan,
  idx_scan,
  seq_scan - idx_scan AS difference
FROM pg_stat_user_tables
WHERE seq_scan > idx_scan
ORDER BY difference DESC;

Resolution

Kill Problematic Queries

SELECT pg_terminate_backend(pid)
FROM pg_stat_activity
WHERE pid = [PID_FROM_ABOVE];

Add Missing Index

CREATE INDEX CONCURRENTLY idx_table_column
ON table_name (column_name);

## Decision Records (ADRs)

### ADR Template

```markdown
# ADR-001: Choose Supabase for Database

## Status
Accepted

## Context
We need a database solution for [Project Name] that supports:
- PostgreSQL compatibility
- Real-time subscriptions
- Built-in authentication
- Easy local development
- Generous free tier

## Decision
We will use Supabase as our primary database and auth provider.

## Alternatives Considered

### PlanetScale
**Pros:**
- Excellent scaling
- Branching for schema changes
- MySQL compatible

**Cons:**
- No built-in auth
- No real-time subscriptions
- Additional services needed

### Firebase
**Pros:**
- Real-time built-in
- Mature platform
- Good mobile SDKs

**Cons:**
- NoSQL (not ideal for our use case)
- Vendor lock-in concerns
- Complex security rules

## Consequences

### Positive
- Single provider for DB + Auth + Storage
- Great developer experience
- Row Level Security for data protection
- Local development with supabase CLI

### Negative
- PostgreSQL-specific features tie us to provider
- Supabase still maturing (some rough edges)
- Limited to their managed offering

### Risks
- Supabase scaling limitations at high traffic
- Migration cost if we need to move

## References
- [Supabase Documentation](https://supabase.com/docs)
- [Comparison: Supabase vs Firebase](https://...)

API Documentation

Endpoint Documentation

# API Reference

## Base URL

Production: https://api.example.com/v1 Staging: https://staging-api.example.com/v1

## Authentication

All API requests require authentication via Bearer token.

```bash
curl -H "Authorization: Bearer YOUR_TOKEN" \
  https://api.example.com/v1/users

Endpoints

Users

Get Current User

GET /users/me

Response:

{
  "id": "usr_123",
  "email": "user@example.com",
  "name": "John Doe",
  "created_at": "2024-01-01T00:00:00Z"
}

Update User

PATCH /users/me

Request Body:

Field	Type	Required	Description
name	string	No	Display name
avatar_url	string	No	Profile image URL

Example:

curl -X PATCH \
  -H "Authorization: Bearer YOUR_TOKEN" \
  -H "Content-Type: application/json" \
  -d '{"name": "Jane Doe"}' \
  https://api.example.com/v1/users/me

Error Responses

Status	Code	Description
400	BAD_REQUEST	Invalid request body
401	UNAUTHORIZED	Missing or invalid token
403	FORBIDDEN	Insufficient permissions
404	NOT_FOUND	Resource not found
429	RATE_LIMITED	Too many requests
500	INTERNAL_ERROR	Server error

Error Response Format:

{
  "error": {
    "code": "NOT_FOUND",
    "message": "User not found"
  }
}

## Environment Documentation

### Environment Matrix

```markdown
# Environments

## Overview

| Environment | URL | Purpose | Deploy |
|-------------|-----|---------|--------|
| Production | https://myapp.com | Live users | Manual (main) |
| Staging | https://staging.myapp.com | Pre-release testing | Auto (main) |
| Preview | https://pr-*.vercel.app | PR review | Auto (PR) |
| Development | http://localhost:3000 | Local dev | Manual |

## Configuration

### Production
```env
NODE_ENV=production
DATABASE_URL=[Supabase Production]
NEXT_PUBLIC_APP_URL=https://myapp.com

Staging

NODE_ENV=production
DATABASE_URL=[Supabase Staging Branch]
NEXT_PUBLIC_APP_URL=https://staging.myapp.com

Development

NODE_ENV=development
DATABASE_URL=[Local Supabase]
NEXT_PUBLIC_APP_URL=http://localhost:3000

Access

Production

• Vercel: Admin only
• Database: Read-only for devs, write for admin
• Logs: All engineers

Staging

• Vercel: All engineers
• Database: All engineers
• Logs: All engineers

Secrets Rotation

Secret	Rotation	Last Rotated
Database password	90 days	2024-01-15
API keys	90 days	2024-01-15
JWT secret	Never	Initial setup

## Documentation-as-Code

### Documentation Structure

docs/ ├── README.md # Documentation index ├── architecture/ │ ├── overview.md # System architecture │ ├── data-flow.md # Data flow diagrams │ └── decisions/ # ADRs │ ├── 001-database.md │ └── 002-hosting.md ├── runbooks/ │ ├── README.md # Runbook index │ ├── database.md # Database issues │ ├── deployment.md # Deployment issues │ └── outage.md # Service outage ├── api/ │ └── reference.md # API documentation └── onboarding/ ├── setup.md # Local setup └── contributing.md # How to contribute

### Auto-Generated Documentation

```yaml
# .github/workflows/docs.yml
name: Generate Docs

on:
  push:
    branches: [main]
    paths:
      - 'src/**'
      - 'docs/**'

jobs:
  generate-docs:
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@v4

      - name: Generate API docs from OpenAPI
        run: |
          npx @redocly/cli build-docs openapi.yaml \
            --output docs/api/index.html

      - name: Generate TypeDoc
        run: npx typedoc --out docs/api/typescript

      - name: Deploy to GitHub Pages
        uses: peaceiris/actions-gh-pages@v3
        with:
          github_token: ${{ secrets.GITHUB_TOKEN }}
          publish_dir: ./docs

Documentation Checklist

Architecture Docs

• System overview diagram
• Component descriptions
• Data flow documentation
• Security architecture
• Technology decisions (ADRs)

Operational Docs

• Runbooks for common issues
• Deployment procedures
• Monitoring and alerting
• Incident response plan
• On-call procedures

Developer Docs

• Local setup guide
• API reference
• Contributing guidelines
• Code conventions
• Testing guide

Maintenance

• Documentation review schedule
• Ownership assigned
• Change process defined
• Versioning strategy

When to Use This Skill

Invoke this skill when:

• Creating architecture documentation
• Writing runbooks for operations
• Documenting decision rationale (ADRs)
• Setting up documentation structure
• Creating onboarding materials
• Building automated documentation
• Planning incident response procedures