Senior Architect

Complete toolkit for senior architect with modern tools and best practices.

Core Capabilities

1. Architecture Diagram Generation

Create clear, maintainable architecture diagrams using Mermaid or ASCII art.

C4 Model Levels:

• •Context: System and external actors
• •Container: Applications, databases, services
• •Component: Internal structure of containers
• •Code: Class/module level (rarely needed)

Mermaid Example:

graph TB
    subgraph "Frontend"
        Web[Web App]
        Mobile[Mobile App]
    end
    
    subgraph "Backend"
        API[API Gateway]
        Auth[Auth Service]
        Core[Core Service]
    end
    
    subgraph "Data"
        DB[(PostgreSQL)]
        Cache[(Redis)]
    end
    
    Web --> API
    Mobile --> API
    API --> Auth
    API --> Core
    Core --> DB
    Core --> Cache

2. System Design Workflow

Step 1: Requirements Gathering

• •Functional requirements (what it does)
• •Non-functional requirements (performance, scale, reliability)
• •Constraints (budget, timeline, existing systems)

Step 2: High-Level Design

• •Identify major components
• •Define data flow
• •Choose communication patterns (sync/async, REST/GraphQL/gRPC)

Step 3: Detailed Design

• •Database schema
• •API contracts
• •Error handling strategy
• •Caching strategy

Step 4: Trade-off Analysis

• •Document alternatives considered
• •Explain why chosen approach wins
• •Note risks and mitigations

3. Dependency Analysis

Analyze project dependencies to understand:

• •Direct vs transitive dependencies
• •Security vulnerabilities
• •Outdated packages
• •License compliance

Commands:

# Node.js
npm ls --all
npm audit
npm outdated

# Python
pip list --outdated
pip-audit
pipdeptree

# Go
go mod graph
go list -m -u all

Architecture Patterns

Monolith

When to use:

• •Early-stage products
• •Small teams (< 10 developers)
• •Simple domain

Structure:

src/
├── api/          # HTTP handlers
├── domain/       # Business logic
├── repository/   # Data access
└── infrastructure/ # External services

Microservices

When to use:

• •Independent scaling requirements
• •Multiple teams with clear boundaries
• •Polyglot requirements

Key concerns:

• •Service discovery
• •Distributed tracing
• •Data consistency (eventual vs strong)
• •API versioning

Event-Driven

When to use:

• •Loose coupling between services
• •Async processing requirements
• •Audit trail needs

Patterns:

• •Event sourcing
• •CQRS (Command Query Responsibility Segregation)
• •Saga pattern for distributed transactions

Tech Stack Decision Framework

Database Selection

API Style Selection

Frontend Framework Selection

Design Principles

SOLID for Architecture

• •Single Responsibility: Each service does one thing well
• •Open/Closed: Extend via configuration, not modification
• •Liskov Substitution: Services honor their contracts
• •Interface Segregation: Small, focused APIs
• •Dependency Inversion: Depend on abstractions

12-Factor App

1. •Codebase: One repo per service
2. •Dependencies: Explicitly declared
3. •Config: Environment variables
4. •Backing services: Treat as attached resources
5. •Build, release, run: Strict separation
6. •Processes: Stateless, share-nothing
7. •Port binding: Self-contained HTTP server
8. •Concurrency: Scale via processes
9. •Disposability: Fast startup, graceful shutdown
10. •Dev/prod parity: Keep environments similar
11. •Logs: Treat as event streams
12. •Admin processes: Run as one-off tasks

Common Anti-Patterns

Distributed Monolith

• •Symptom: Services tightly coupled, deploy together
• •Fix: Define clear boundaries, async communication

Big Ball of Mud

• •Symptom: No clear structure, everything depends on everything
• •Fix: Introduce layers, enforce boundaries

Golden Hammer

• •Symptom: Using one tool for everything
• •Fix: Choose tools based on requirements

Premature Optimization

• •Symptom: Complex architecture for simple problems
• •Fix: Start simple, evolve based on real needs

Performance Considerations

Caching Strategy

Cache Locations:

• •Browser (HTTP cache headers)
• •CDN (static assets, API responses)
• •Application (Redis, in-memory)
• •Database (query cache)

Cache Invalidation:

• •Time-based (TTL)
• •Event-based (pub/sub)
• •Write-through vs write-behind

Database Optimization

Indexing:

• •Index columns used in WHERE, JOIN, ORDER BY
• •Composite indexes for multi-column queries
• •Avoid over-indexing (slows writes)

Query Optimization:

• •Use EXPLAIN ANALYZE
• •Avoid N+1 queries
• •Use connection pooling

Scaling Patterns

Vertical: Bigger machines (easy but limited) Horizontal: More machines (complex but scalable)

Read scaling: Read replicas, caching Write scaling: Sharding, partitioning

Security Checklist

Authentication

• • Use proven libraries (passport, next-auth, better-auth)
• • Secure session management
• • MFA for sensitive operations

Authorization

• • RBAC or ABAC implementation
• • Principle of least privilege
• • API key rotation

Data Protection

• • Encrypt at rest and in transit
• • PII handling compliant
• • Audit logging

Infrastructure

• • Network segmentation
• • Secrets management (Vault, AWS Secrets Manager)
• • Regular security scanning

Documentation Templates

Architecture Decision Record (ADR)

# ADR-001: Choose PostgreSQL for primary database

## Status
Accepted

## Context
We need a primary database for user data and transactions.

## Decision
Use PostgreSQL with Prisma ORM.

## Consequences
- Pro: Strong consistency, mature ecosystem
- Pro: JSON support for flexible schemas
- Con: Horizontal scaling requires more effort

API Contract

openapi: 3.0.0
info:
  title: User Service
  version: 1.0.0
paths:
  /users/{id}:
    get:
      summary: Get user by ID
      parameters:
        - name: id
          in: path
          required: true
          schema:
            type: string
      responses:
        200:
          description: User found
        404:
          description: User not found

Quick Commands

# Development
npm run dev
npm run build
npm run test
npm run lint

# Analysis
npx depcheck              # Find unused dependencies
npx madge --circular src  # Find circular dependencies
npx bundle-size           # Analyze bundle size

# Deployment
docker build -t app:latest .
docker-compose up -d
kubectl apply -f k8s/