Senior Architect

---
name: senior-architect
description: This skill should be used when the user asks to "design system architecture", "evaluate microservices vs monolith", "create architecture diagrams", "analyze dependencies", "choose a database", "plan for scalability", "make technical decisions", or "review system design". Use for architecture decision records (ADRs), tech stack evaluation, system design reviews, dependency analysis, and generating architecture diagrams in Mermaid, PlantUML, or ASCII format.
---

# Senior Architect

Architecture design and analysis tools for making informed technical decisions.

## Table of Contents

- [Quick Start](#quick-start)
- [Tools Overview](#tools-overview)
  - [Architecture Diagram Generator](#1-architecture-diagram-generator)
  - [Dependency Analyzer](#2-dependency-analyzer)
  - [Project Architect](#3-project-architect)
- [Decision Workflows](#decision-workflows)
  - [Database Selection](#database-selection-workflow)
  - [Architecture Pattern Selection](#architecture-pattern-selection-workflow)
  - [Monolith vs Microservices](#monolith-vs-microservices-decision)
- [Reference Documentation](#reference-documentation)
- [Tech Stack Coverage](#tech-stack-coverage)
- [Common Commands](#common-commands)

---

## Quick Start

```bash
# Generate architecture diagram from project
python scripts/architecture_diagram_generator.py ./my-project --format mermaid

# Analyze dependencies for issues
python scripts/dependency_analyzer.py ./my-project --output json

# Get architecture assessment
python scripts/project_architect.py ./my-project --verbose
```

---

## Tools Overview

### 1. Architecture Diagram Generator

Generates architecture diagrams from project structure in multiple formats.

**Solves:** "I need to visualize my system architecture for documentation or team discussion"

**Input:** Project directory path
**Output:** Diagram code (Mermaid, PlantUML, or ASCII)

**Supported diagram types:**
- `component` - Shows modules and their relationships
- `layer` - Shows architectural layers (presentation, business, data)
- `deployment` - Shows deployment topology

**Usage:**
```bash
# Mermaid format (default)
python scripts/architecture_diagram_generator.py ./project --format mermaid --type component

# PlantUML format
python scripts/architecture_diagram_generator.py ./project --format plantuml --type layer

# ASCII format (terminal-friendly)
python scripts/architecture_diagram_generator.py ./project --format ascii

# Save to file
python scripts/architecture_diagram_generator.py ./project -o architecture.md
```

**Example output (Mermaid):**
```mermaid
graph TD
    A[API Gateway] --> B[Auth Service]
    A --> C[User Service]
    B --> D[(PostgreSQL)]
    C --> D
```

---

### 2. Dependency Analyzer

Analyzes project dependencies for coupling, circular dependencies, and outdated packages.

**Solves:** "I need to understand my dependency tree and identify potential issues"

**Input:** Project directory path
**Output:** Analysis report (JSON or human-readable)

**Analyzes:**
- Dependency tree (direct and transitive)
- Circular dependencies between modules
- Coupling score (0-100)
- Outdated packages

**Supported package managers:**
- npm/yarn (`package.json`)
- Python (`requirements.txt`, `pyproject.toml`)
- Go (`go.mod`)
- Rust (`Cargo.toml`)

**Usage:**
```bash
# Human-readable report
python scripts/dependency_analyzer.py ./project

# JSON output for CI/CD integration
python scripts/dependency_analyzer.py ./project --output json

# Check only for circular dependencies
python scripts/dependency_analyzer.py ./project --check circular

# Verbose mode with recommendations
python scripts/dependency_analyzer.py ./project --verbose
```

**Example output:**
```
Dependency Analysis Report
==========================
Total dependencies: 47 (32 direct, 15 transitive)
Coupling score: 72/100 (moderate)

Issues found:
- CIRCULAR: auth → user → permissions → auth
- OUTDATED: lodash 4.17.15 → 4.17.21 (security)

Recommendations:
1. Extract shared interface to break circular dependency
2. Update lodash to fix CVE-2020-8203
```

---

### 3. Project Architect

Analyzes project structure and detects architectural patterns, code smells, and improvement opportunities.

**Solves:** "I want to understand the current architecture and identify areas for improvement"

**Input:** Project directory path
**Output:** Architecture assessment report

**Detects:**
- Architectural patterns (MVC, layered, hexagonal, microservices indicators)
- Code organization issues (god classes, mixed concerns)
- Layer violations
- Missing architectural components

**Usage:**
```bash
# Full assessment
python scripts/project_architect.py ./project

# Verbose with detailed recommendations
python scripts/project_architect.py ./project --verbose

# JSON output
python scripts/project_architect.py ./project --output json

# Check specific aspect
python scripts/project_architect.py ./project --check layers
```

**Example output:**
```
Architecture Assessment
=======================
Detected pattern: Layered Architecture (confidence: 85%)

Structure analysis:
  ✓ controllers/  - Presentation layer detected
  ✓ services/     - Business logic layer detected
  ✓ repositories/ - Data access layer detected
  ⚠ models/       - Mixed domain and DTOs

Issues:
- LARGE FILE: UserService.ts (1,847 lines) - consider splitting
- MIXED CONCERNS: PaymentController contains business logic

Recommendations:
1. Split UserService into focused services
2. Move business logic from controllers to services
3. Separate domain models from DTOs
```

---

## Decision Workflows

### Database Selection Workflow

Use when choosing a database for a new project or migrating existing data.

**Step 1: Identify data characteristics**
| Characteristic | Points to SQL | Points to NoSQL |
|----------------|---------------|-----------------|
| Structured with relationships | ✓ | |
| ACID transactions required | ✓ | |
| Flexible/evolving schema | | ✓ |
| Document-oriented data | | ✓ |
| Time-series data | | ✓ (specialized) |

**Step 2: Evaluate scale requirements**
- <1M records, single region → PostgreSQL or MySQL
- 1M-100M records, read-heavy → PostgreSQL with read replicas
- >100M records, global distribution → CockroachDB, Spanner, or DynamoDB
- High write throughput (>10K/sec) → Cassandra or ScyllaDB

**Step 3: Check consistency requirements**
- Strong consistency required → SQL or CockroachDB
- Eventual consistency acceptable → DynamoDB, Cassandra, MongoDB

**Step 4: Document decision**
Create an ADR (Architecture Decision Record) with:
- Context and requirements
- Options considered
- Decision and rationale
- Trade-offs accepted

**Quick reference:**
```
PostgreSQL → Default choice for most applications
MongoDB    → Document store, flexible schema
Redis      → Caching, sessions, real-time features
DynamoDB   → Serverless, auto-scaling, AWS-native
TimescaleDB → Time-series data with SQL interface
```

---

### Architecture Pattern Selection Workflow

Use when designing a new system or refactoring existing architecture.

**Step 1: Assess team and project size**
| Team Size | Recommended Starting Point |
|-----------|---------------------------|
| 1-3 developers | Modular monolith |
| 4-10 developers | Modular monolith or service-oriented |
| 10+ developers | Consider microservices |

**Step 2: Evaluate deployment requirements**
- Single deployment unit acceptable → Monolith
- Independent scaling needed → Microservices
- Mixed (some services scale differently) → Hybrid

**Step 3: Consider data boundaries**
- Shared database acceptable → Monolith or modular monolith
- Strict data isolation required → Microservices with separate DBs
- Event-driven communication fits → Event-sourcing/CQRS

**Step 4: Match pattern to requirements**

| Requirement | Recommended Pattern |
|-------------|-------------------|
| Rapid MVP development | Modular Monolith |
| Independent team deployment | Microservices |
| Complex domain logic | Domain-Driven Design |
| High read/write ratio difference | CQRS |
| Audit trail required | Event Sourcing |
| Third-party integrations | Hexagonal/Ports & Adapters |

See `references/architecture_patterns.md` for detailed pattern descriptions.

---

### Monolith vs Microservices Decision

**Choose Monolith when:**
- [ ] Team is small (<10 developers)
- [ ] Domain boundaries are unclear
- [ ] Rapid iteration is priority
- [ ] Operational complexity must be minimized
- [ ] Shared database is acceptable

**Choose Microservices when:**
- [ ] Teams can own services end-to-end
- [ ] Independent deployment is critical
- [ ] Different scaling requirements per component
- [ ] Technology diversity is needed
- [ ] Domain boundaries are well understood

**Hybrid approach:**
Start with a modular monolith. Extract services only when:
1. A module has significantly different scaling needs
2. A team needs independent deployment
3. Technology constraints require separation

---

## Reference Documentation

Load these files for detailed information:

| File | Contains | Load when user asks about |
|------|----------|--------------------------|
| `references/architecture_patterns.md` | 9 architecture patterns with trade-offs, code examples, and when to use | "which pattern?", "microservices vs monolith", "event-driven", "CQRS" |
| `references/system_design_workflows.md` | 6 step-by-step workflows for system design tasks | "how to design?", "capacity planning", "API design", "migration" |
| `references/tech_decision_guide.md` | Decision matrices for technology choices | "which database?", "which framework?", "which cloud?", "which cache?" |

---

## Tech Stack Coverage

**Languages:** TypeScript, JavaScript, Python, Go, Swift, Kotlin, Rust
**Frontend:** React, Next.js, Vue, Angular, React Native, Flutter
**Backend:** Node.js, Express, FastAPI, Go, GraphQL, REST
**Databases:** PostgreSQL, MySQL, MongoDB, Redis, DynamoDB, Cassandra
**Infrastructure:** Docker, Kubernetes, Terraform, AWS, GCP, Azure
**CI/CD:** GitHub Actions, GitLab CI, CircleCI, Jenkins

---

## Common Commands

```bash
# Architecture visualization
python scripts/architecture_diagram_generator.py . --format mermaid
python scripts/architecture_diagram_generator.py . --format plantuml
python scripts/architecture_diagram_generator.py . --format ascii

# Dependency analysis
python scripts/dependency_analyzer.py . --verbose
python scripts/dependency_analyzer.py . --check circular
python scripts/dependency_analyzer.py . --output json

# Architecture assessment
python scripts/project_architect.py . --verbose
python scripts/project_architect.py . --check layers
python scripts/project_architect.py . --output json
```

---

## Getting Help

1. Run any script with `--help` for usage information
2. Check reference documentation for detailed patterns and workflows
3. Use `--verbose` flag for detailed explanations and recommendations