---
id: wiki-2026-0508-island-architecture
title: Island Architecture
category: 10_Wiki/Topics
status: verified
canonical_id: self
aliases: [Islands Architecture, Partial Hydration, Selective Hydration]
duplicate_of: none
source_trust_level: A
confidence_score: 0.9
verification_status: applied
tags: [architecture, web, frontend, hydration, performance]
raw_sources: []
last_reinforced: 2026-05-10
github_commit: pending
tech_stack:
  language: typescript
  framework: astro-fresh
---

# Island Architecture

## 매 한 줄
> **"매 mostly-static HTML 의 sea 의 isolated interactive 'island' 의 selective hydration 의 통한 ship-less-JS"**. 매 Katie Sylor-Miller (2019) 의 term, Jason Miller (2020) 의 popularization, 매 Astro (2021) / Fresh (Deno) / Marko / Qwik 의 implementation — 매 SPA-everything 의 over-hydration 의 backlash.

## 매 핵심

### 매 핵심 idea
- Server 의 HTML 의 render (default).
- 매 interactive component (island) 의 isolated hydration boundary.
- 매 island 의 own JS bundle, 매 nothing else 의 ship.
- 매 island 간 의 share state 의 X (or framework-specific signal).

### 매 Hydration directive (Astro)
- `client:load` — 매 page load 의 즉시.
- `client:idle` — `requestIdleCallback`.
- `client:visible` — IntersectionObserver.
- `client:media="(min-width: 768px)"` — viewport conditional.
- `client:only="react"` — server render skip, client only.

### 매 응용
1. Content sites (blog, docs, marketing).
2. E-commerce (정적 product page + interactive cart island).
3. News / publishing (정적 article + comment island).

## 💻 패턴

### Astro — React Island
```astro
---
// src/pages/index.astro
import Counter from '../components/Counter.tsx';
import Newsletter from '../components/Newsletter.tsx';
const posts = await fetch(import.meta.env.CMS_URL).then(r => r.json());
---
<html>
  <body>
    <h1>Blog</h1>
    <ul>{posts.map(p => <li>{p.title}</li>)}</ul>

    <Counter client:visible />               <!-- island, lazy hydrate -->
    <Newsletter client:idle />               <!-- island, idle hydrate -->
  </body>
</html>
```

### Astro — Mixed Frameworks (one page, multiple)
```astro
---
import VueWidget from './Widget.vue';
import SvelteChart from './Chart.svelte';
import SolidSearch from './Search.tsx';
---
<VueWidget client:load />
<SvelteChart client:visible />
<SolidSearch client:idle />
```

### Fresh (Deno) — Island
```tsx
// islands/Counter.tsx
import { useSignal } from '@preact/signals';
export default function Counter() {
  const count = useSignal(0);
  return <button onClick={() => count.value++}>{count.value}</button>;
}

// routes/index.tsx
import Counter from '../islands/Counter.tsx';
export default function Home() {
  return <main><h1>Home</h1><Counter /></main>;
}
```

### Qwik — Resumability (zero hydration)
```tsx
// src/routes/index.tsx
import { component$, useSignal } from '@builder.io/qwik';
export default component$(() => {
  const count = useSignal(0);
  return (
    <button onClick$={() => count.value++}>
      Clicks: {count.value}
    </button>
  );
});
// 매 click 의 시 의 only 의 download — true progressive
```

### Marko 5 — Streaming Islands
```marko
<!doctype html>
<html>
  <body>
    <h1>Products</h1>
    <await(productPromise)>
      <@then|products|>
        <for|p| of=products>
          <product-card p=p/>
        </for>
      </@then>
    </await>
  </body>
</html>
```

### Performance Budget Check
```yaml
# .lighthouserc.yml
ci:
  collect: { url: ['https://example.com/'] }
  assert:
    assertions:
      total-byte-weight: ['error', { maxNumericValue: 200000 }]
      total-blocking-time: ['error', { maxNumericValue: 200 }]
      interaction-to-next-paint: ['error', { maxNumericValue: 200 }]
```

## 매 결정 기준
| 상황 | Approach |
|---|---|
| Content-heavy, low interactivity | Astro (default) |
| Per-route framework choice | Astro multi-framework |
| Edge / Deno preference | Fresh |
| App-shell SPA feel | Next.js / Remix (RSC + Suspense) |
| Zero-hydration target | Qwik |

**기본값**: 매 marketing/blog/docs — Astro + island per interactive component. 매 dashboard-y app — Next.js RSC.

## 🔗 Graph
- 부모: [[Web-Rendering-Strategies]] · [[Frontend-Architecture]]
- 변형: [[Partial-Hydration]] · [[Resumability]] · [[Streaming-SSR]]
- 응용: [[Astro]] · [[Fresh]] · [[Qwik]] · [[Marko]]
- Adjacent: [[React-Server-Components]] · [[Incremental-Static-Regeneration-ISR]] · [[MPA]]

## 🤖 LLM 활용
**언제**: page 의 island boundary 의 propose, hydration directive 의 select, JS bundle 의 reduction 의 suggest.
**언제 X**: 매 framework 의 final choice (team skill, ecosystem fit 의 human decision).

## ❌ 안티패턴
- **Island sprawl**: 매 component 의 `client:load` → SPA equivalent.
- **Cross-island state**: 매 island 의 shared store 의 hack — 매 framework boundary 의 violation.
- **Server-only data 의 island leak**: secret/PII 의 client island prop 의 pass.
- **`client:only` overuse**: server render 의 skip → SEO 의 hurt + LCP 의 regress.
- **Wrong tool**: 매 highly interactive app (Figma-like) 의 Astro 의 force-fit.

## 🧪 검증 / 중복
- Verified (Jason Miller "Islands Architecture" 2020, Astro 4 docs, Fresh docs, web.dev).
- 신뢰도 A.

## 🕓 Changelog
| 날짜 | 변경 |
|---|---|
| 2026-05-08 | Phase 1 |
| 2026-05-10 | Manual cleanup — island architecture (Astro/Fresh/Qwik) 의 full content |
