---
id: wiki-2026-0508-incremental-build
title: Incremental Build
category: 10_Wiki/Topics
status: verified
canonical_id: self
aliases: [Incremental Compilation, Cached Build, Build Cache]
duplicate_of: none
source_trust_level: A
confidence_score: 0.9
verification_status: applied
tags: [build, ci, performance, monorepo, caching]
raw_sources: []
last_reinforced: 2026-05-10
github_commit: pending
tech_stack:
  language: typescript
  framework: turborepo
---

# Incremental Build

## 매 한 줄
> **"매 변경된 파일 + downstream 의존성만 rebuild — 매 hash-based caching 의 핵심"**. 매 1979 Make 의 mtime-based 시작, 매 2026 Turborepo/Nx/Bazel 의 content-addressed cache 가 default — 매 monorepo 에서 100x speedup 흔함.

## 매 핵심

### 매 작동 원리
- **Input hash**: 매 source files + deps + env → SHA256.
- **Cache key**: hash → output artifacts (dist/, .d.ts).
- **Hit**: cache 존재 → restore, skip work.
- **Miss**: rebuild, store.

### 매 granularity
- **File-level**: tsc --incremental (.tsbuildinfo).
- **Task-level**: Turborepo (per-package).
- **Action-level**: Bazel (per-rule, hermetic).

### 매 응용
1. Monorepo CI: 매 affected package 만 test.
2. Local dev: watch mode, 매 sub-second rebuild.
3. Docker: layer caching = path 별 invalidation.

## 💻 패턴

### Turborepo pipeline
```json
// turbo.json
{
  "$schema": "https://turbo.build/schema.json",
  "globalDependencies": ["tsconfig.base.json"],
  "tasks": {
    "build": {
      "dependsOn": ["^build"],
      "inputs": ["src/**", "package.json", "tsconfig.json"],
      "outputs": ["dist/**", ".next/**"],
      "cache": true
    },
    "test": {
      "dependsOn": ["build"],
      "inputs": ["src/**", "test/**"],
      "outputs": ["coverage/**"]
    },
    "lint": { "cache": true, "outputs": [] }
  },
  "remoteCache": { "signature": true }
}
```

### TypeScript incremental
```json
// tsconfig.json
{
  "compilerOptions": {
    "incremental": true,
    "tsBuildInfoFile": ".cache/tsbuild.json",
    "composite": true,
    "declaration": true,
    "declarationMap": true
  },
  "references": [
    { "path": "../core" },
    { "path": "../utils" }
  ]
}
```

### Nx affected
```bash
# Only test packages affected by changes since main
nx affected --target=test --base=origin/main --head=HEAD --parallel=4

# Print affected graph
nx graph --affected --base=origin/main
```

### Vite HMR (sub-second)
```ts
// vite.config.ts
import { defineConfig } from 'vite';
export default defineConfig({
  server: {
    hmr: { overlay: true },
    watch: { usePolling: false, ignored: ['**/node_modules/**', '**/dist/**'] }
  },
  build: {
    rollupOptions: { cache: true }
  },
  cacheDir: '.cache/vite'
});
```

### GitHub Actions remote cache
```yaml
- uses: actions/cache@v4
  with:
    path: |
      .turbo
      node_modules/.cache
    key: turbo-${{ runner.os }}-${{ hashFiles('**/pnpm-lock.yaml') }}-${{ github.sha }}
    restore-keys: turbo-${{ runner.os }}-${{ hashFiles('**/pnpm-lock.yaml') }}-

- run: pnpm turbo run build test --cache-dir=.turbo
```

### Bazel hermetic action
```python
# BUILD.bazel
load("@npm//@bazel/typescript:index.bzl", "ts_project")
ts_project(
    name = "core",
    srcs = glob(["src/**/*.ts"]),
    declaration = True,
    incremental = True,
    deps = ["//packages/utils"],
)
```

### Cache hit ratio metric
```ts
// scripts/cache-stats.ts
import { execSync } from 'node:child_process';
const out = execSync('turbo run build --dry=json').toString();
const tasks = JSON.parse(out).tasks;
const hits = tasks.filter((t: any) => t.cache.status === 'HIT').length;
console.log(`cache hit: ${hits}/${tasks.length} = ${(hits/tasks.length*100).toFixed(1)}%`);
```

## 매 결정 기준
| 상황 | Approach |
|---|---|
| Monorepo 10+ packages | Turborepo or Nx |
| Strict reproducibility | Bazel (hermetic) |
| Single TS app | tsc --incremental + Vite |
| Docker images | BuildKit + multi-stage layer cache |

**기본값**: 매 Turborepo + remote cache (Vercel or self-hosted).

## 🔗 Graph
- 부모: [[Continuous Integration]]
- 응용: [[CI_CD_Pipeline]]
- Adjacent: [[Dependency Graph]]

## 🤖 LLM 활용
**언제**: 매 turbo.json/nx.json 의 generation, cache key tuning 추천.
**언제 X**: 매 Bazel hermetic rule — 매 strict, LLM hallucination 위험.

## ❌ 안티패턴
- **Time-based keys**: `date +%s` cache key — 매 hit 0%.
- **Untracked inputs**: env var, system clock 의존 → false hit.
- **Cache everything**: lint output 까지 cache → debugging 의 hell.
- **No remote cache**: CI 매 fresh 시작 → local-only 의 무의미.

## 🧪 검증 / 중복
- Verified (Turborepo 2.x, Nx 20+, Bazel 7+ 공식 docs).
- 신뢰도 A.

## 🕓 Changelog
| 날짜 | 변경 |
|---|---|
| 2026-05-08 | Phase 1 |
| 2026-05-10 | Manual cleanup — incremental build 의 hash caching 정리 |
