2nd/10_Wiki/Topics/AI_and_ML/Software Architecture Pattern.md

---
id: wiki-2026-0508-software-architecture-pattern
title: Software Architecture Pattern
category: 10_Wiki/Topics
status: verified
canonical_id: self
aliases: [Architecture Patterns, System Design Patterns]
duplicate_of: none
source_trust_level: A
confidence_score: 0.9
verification_status: applied
tags: [architecture, patterns, system-design, microservices, serverless]
raw_sources: []
last_reinforced: 2026-05-10
github_commit: pending
tech_stack:
  language: multi
  framework: kubernetes/serverless/edge
---

# Software Architecture Pattern

## 매 한 줄
> **"매 architecture pattern 의 problem-driven choice — layered (CRUD), microservices (org / scale), event-driven (decouple), hexagonal (testability), serverless / edge (ops scale)"**. 매 2026 의 reality 의 hybrid — modular monolith + selective microservices + event backbone (Kafka / NATS) + edge (Cloudflare Workers / Deno Deploy / Vercel). 매 single-pattern dogma X — 매 trade-off 의 explicit.

## 매 핵심

### 매 Major patterns
- **Layered (n-tier)**: presentation / business / data — 매 CRUD default.
- **Microservices**: 매 service 의 independent deploy + own DB.
- **Event-driven (EDA)**: 매 producer-consumer + queue / log.
- **Hexagonal (ports & adapters)**: 매 domain 의 IO 의 isolate.
- **CQRS + Event Sourcing**: read / write split, append-only event.
- **Modular Monolith**: 매 monolith 위 의 boundary — 매 underrated 2026 default.
- **Serverless**: FaaS, 매 ops-zero, cold-start trade.
- **Edge / Distributed**: 매 user-near, 매 SQLite-replicated (Turso, D1).

### 매 Cross-cutting
- **API Gateway**: 매 frontend의 single entry.
- **BFF**: 매 client-specific aggregator.
- **Saga**: 매 distributed transaction.
- **Outbox**: 매 db + event 의 atomic publish.
- **CRDT**: 매 multi-region eventual consistency.

### 매 Modern (2026) trends
- **Modular monolith** 의 first — 매 microservices 의 premature 의 X.
- **Edge runtime** (Workers, Lambda@Edge) 의 read path.
- **AI-augmented architect** — Claude / GPT-5 의 ADR draft / pattern fit review.
- **Event streaming default** — Kafka / Redpanda / NATS JetStream.

### 매 응용
1. SaaS multi-tenant — modular monolith + tenant DB.
2. E-commerce — microservices + saga + event backbone.
3. Real-time collab — CRDT + edge + WebSocket.
4. AI app — gateway + queue + worker (LLM inference).

## 💻 패턴

### Hexagonal (ports & adapters, Python)
```python
from typing import Protocol

# 매 port (domain interface)
class OrderRepo(Protocol):
    def save(self, order: "Order") -> None: ...
    def by_id(self, id: str) -> "Order | None": ...

# 매 domain (pure)
class Order:
    def __init__(self, id, items): self.id, self.items = id, items
    def total(self): return sum(i.price for i in self.items)

class PlaceOrder:
    def __init__(self, repo: OrderRepo): self.repo = repo
    def __call__(self, order: Order):
        if order.total() <= 0: raise ValueError("empty")
        self.repo.save(order)

# 매 adapter (Postgres impl) — 매 domain 의 zero coupling
class PgOrderRepo:
    def __init__(self, conn): self.conn = conn
    def save(self, order): self.conn.execute("INSERT ...", ...)
    def by_id(self, id): ...
```

### CQRS + Event Sourcing (skeleton)
```python
from dataclasses import dataclass

@dataclass(frozen=True)
class OrderPlaced: order_id: str; total: float

class OrderAggregate:
    def __init__(self):
        self.id = None; self.total = 0
    def apply(self, event):
        if isinstance(event, OrderPlaced):
            self.id = event.order_id; self.total = event.total

class EventStore:
    def __init__(self): self.events = []
    def append(self, e): self.events.append(e)
    def load(self, id):
        agg = OrderAggregate()
        for e in self.events:
            if getattr(e, "order_id", None) == id: agg.apply(e)
        return agg
```

### Outbox pattern (atomic db + event)
```sql
BEGIN;
INSERT INTO orders (id, total) VALUES ('o1', 100);
INSERT INTO outbox (aggregate_id, type, payload, created_at)
  VALUES ('o1', 'OrderPlaced', '{"id":"o1","total":100}', NOW());
COMMIT;

-- 매 worker 의 outbox 의 poll → Kafka publish → mark sent
```

### Saga (orchestration, TypeScript)
```typescript
async function placeOrderSaga(order: Order) {
  const compensations: (() => Promise<void>)[] = [];
  try {
    await reserveStock(order);
    compensations.push(() => releaseStock(order));
    await chargePayment(order);
    compensations.push(() => refund(order));
    await scheduleShipment(order);
  } catch (e) {
    for (const c of compensations.reverse()) await c().catch(() => {});
    throw e;
  }
}
```

### Edge handler (Cloudflare Workers + D1)
```typescript
export default {
  async fetch(req: Request, env: { DB: D1Database }) {
    const url = new URL(req.url);
    if (url.pathname === "/api/post" && req.method === "GET") {
      const id = url.searchParams.get("id")!;
      const row = await env.DB.prepare("SELECT * FROM posts WHERE id = ?")
        .bind(id).first();
      return Response.json(row, {
        headers: { "cache-control": "public, max-age=60, s-maxage=300" },
      });
    }
    return new Response("not found", { status: 404 });
  },
};
```

### Modular Monolith (Go module structure)
```
cmd/api/main.go
internal/
  billing/        # 매 module — own domain, own table prefix
    api.go
    domain.go
    repo.go
  catalog/
    api.go
    ...
  shared/
    events.go     # 매 cross-module event bus
```

### Event-driven (NATS JetStream)
```typescript
import { connect, JSONCodec } from "nats";
const nc = await connect({ servers: "nats://nats:4222" });
const js = nc.jetstream();
const jc = JSONCodec();

// publish
await js.publish("orders.placed", jc.encode({ id: "o1", total: 100 }));

// subscribe (durable consumer)
const c = await js.consumers.get("ORDERS", "ship-worker");
const iter = await c.consume();
for await (const m of iter) {
  await ship(jc.decode(m.data));
  m.ack();
}
```

### API Gateway (Kong declarative)
```yaml
_format_version: "3.0"
services:
  - name: orders
    url: http://orders.internal:8080
    routes: [{ paths: ["/orders"], strip_path: false }]
    plugins:
      - name: rate-limiting
        config: { minute: 60, policy: redis, redis_host: redis }
      - name: jwt
```

## 매 결정 기준
| 상황 | Pattern |
|---|---|
| Small team, CRUD | Layered or Modular Monolith |
| Org scaling, 매 indep deploy | Microservices (with care) |
| Audit / replay | Event Sourcing + CQRS |
| Read-heavy global | Edge + cache |
| Distributed transactions | Saga + Outbox |
| Real-time collab | CRDT + WebSocket |
| Spiky / unpredictable | Serverless |

**기본값**: Modular Monolith first. 매 split 의 evidence-driven (org boundary + perf SLO).

## 🔗 Graph
- 부모: [[System-Design]]
- 변형: [[Microservices]] · [[Event-Driven-Architecture]] · [[Hexagonal Architecture]] · [[CQRS]]
- 응용: [[Modular Monolith]]
- Adjacent: [[API-Gateway]] · [[Service Mesh]] · [[Edge Computing|Edge-Computing]]

## 🤖 LLM 활용
**언제**: ADR draft, 매 pattern fit review (problem → pattern recommendation), trade-off matrix generate.
**언제 X**: actual capacity planning (load test), team-specific tech-stack lock-in (org context).

## ❌ 안티패턴
- **Premature microservices**: 매 distributed monolith — 매 worst.
- **Distributed transaction (2PC)**: 매 saga 의 use.
- **Shared DB across services**: 매 microservices 의 violate.
- **No outbox**: 매 dual-write inconsistency.
- **Pattern dogma**: 매 trade-off 의 explicit X.

## 🧪 검증 / 중복
- Verified (Fowler, Vernon, Newman, Richardson architecture references).
- 신뢰도 A.

## 🕓 Changelog
| 날짜 | 변경 |
|---|---|
| 2026-05-08 | Phase 1 |
| 2026-05-10 | Manual cleanup — full pattern catalog with code examples |