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

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

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 createdat } projects ||--o{ tasks : contains projects { uuid id PK uuid userid FK text name text status } tasks { uuid id PK uuid project_id FK text title boolean completed }

Runbooks

Runbook Template

# 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

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 pgstatactivity;

Kill idle connections

SELECT pgterminatebackend(pid) FROM pgstatactivity 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](https://dashboard.example.com)
- [Logs](https://logs.example.com)
- [Metrics](https://metrics.example.com)

Database Runbooks

# Runbook: Database Performance Issues

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

## Quick Checks

### 1. Check Active Connections

SELECT state, count(*), max(now() - querystart) as maxduration FROM pgstatactivity GROUP BY state;

### 2. Find Long-Running Queries

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

### 3. Check Table Sizes

SELECT schemaname, tablename, pgsizepretty(pgtotalrelationsize(schemaname || '.' || tablename)) as size FROM pgtables WHERE schemaname = 'public' ORDER BY pgtotalrelation_size(schemaname || '.' || tablename) DESC LIMIT 10;

### 4. Check Missing Indexes

SELECT relname, seqscan, idxscan, seqscan - idxscan AS difference FROM pgstatusertables WHERE seqscan > idx_scan ORDER BY difference DESC;

## Resolution

### Kill Problematic Queries

SELECT pgterminatebackend(pid) FROM pgstatactivity WHERE pid = [PIDFROMABOVE];

### Add Missing Index

CREATE INDEX CONCURRENTLY idxtablecolumn ON tablename (columnname);

Decision Records (ADRs)

ADR Template

# 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.

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

## Endpoints

### Users

#### Get Current User

GET /users/me

**Response:**

{ "id": "usr123", "email": "[email protected]", "name": "John Doe", "createdat": "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

# 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

NODEENV=production DATABASEURL=[Supabase Production] NEXTPUBLICAPP_URL=https://myapp.com

### Staging

NODEENV=production DATABASEURL=[Supabase Staging Branch] NEXTPUBLICAPP_URL=https://staging.myapp.com

### Development

NODEENV=development DATABASEURL=[Local Supabase] NEXTPUBLICAPP_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

# .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