Lesson 23: Mono-Repo vs Multi-Repo — Source Code Organization

Microservices & Micro Frontend system design — From basics to Production

Part 8: CI/CD & Deployment Strategies

xdev.asia

Introduction

The way source code is organized determines developer experience, CI/CD complexity, and team collaboration. This article compares Mono-Repo vs Multi-Repo and provides guidance on choosing the right one.

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1. Multi-Repo

1.1 Model

github.com/company/
├── product-service/       (repo riêng)
├── order-service/         (repo riêng)
├── cart-service/          (repo riêng)
├── product-mfe/           (repo riêng)
├── cart-mfe/              (repo riêng)
├── shell-app/             (repo riêng)
├── shared-ui/             (repo riêng, npm package)
└── shared-types/          (repo riêng, npm package)

1.2 Advantages & Disadvantages

Advantages	Disadvantages
Clear ownership	Shared code is difficult to manage (npm publish)
Independent CI/CD	Complex cross-repo changes
Smaller repos = fast clone	Dependency version drift
Fine-grained access control	Consistency is difficult to enforce

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2. Mono-Repo

2.1 Model

github.com/company/platform/
├── apps/
│   ├── shell-app/
│   ├── product-mfe/
│   ├── cart-mfe/
│   └── order-mfe/
├── services/
│   ├── product-service/
│   ├── order-service/
│   └── cart-service/
├── packages/
│   ├── shared-ui/
│   ├── shared-types/
│   └── eslint-config/
├── turbo.json / nx.json
└── package.json (workspace root)

2.2 Advantages & Disadvantages

Advantages	Disadvantages
Shared code easily (internal packages)	Large repo → slow clone
Atomic cross-package changes	CI complexity (affected detection)
Consistent tooling & configurations	Access control coarse-grained
Refactoring is easy	Build time long (need caching)

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3. Decision Matrix

Factor	Multi-Repo	Mono-Repo
Team size	50+ devs, many teams	< 50 devs, few teams
Shared code	Less shared	Many shared packages
Deploy independence	✅ Natural	✅ With affected detection
Cross-cutting changes	❌ Multiple PRs	✅ Single PR
CI/CD	Simple per repo	Complex but powerful
Onboarding	Easy (1 service/repo)	Medium (big repo)

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4. Mono-Repo Tools

4.1 Turborepo

// turbo.json
{
  "pipeline": {
    "build": {
      "dependsOn": ["^build"],
      "outputs": ["dist/**", ".next/**"]
    },
    "test": {
      "dependsOn": ["build"]
    },
    "lint": {}
  }
}

# Build chỉ affected packages
turbo build --filter=...[origin/main]

# Build product-mfe và dependencies
turbo build --filter=product-mfe...

4.2 Nx

# Affected commands (chỉ build/test code thay đổi)
nx affected --target=build --base=main
nx affected --target=test --base=main

# Dependency graph
nx graph

4.3 Key Features

Features	Turborepo	Nx
Affected detection	✅ Git-based	✅ Dependency graph
Remote caching	✅ Vercel	✅ Nx Cloud
Task orchestration	✅ Pipelines	✅ Task graph
Code generation	❌	✅ Generators
Plugin ecosystem	Limited	Rich (React, Node, etc.)

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5. Code Ownership (CODEOWNERS)

# .github/CODEOWNERS
apps/product-mfe/    @team-product
apps/cart-mfe/       @team-cart
services/product-*/  @team-product
services/order-*/    @team-order
packages/shared-ui/  @team-platform
packages/shared-*/   @team-platform
turbo.json           @team-platform

→ PR automatically assign reviewers based on changed files.

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6. Recommendations

E-Commerce Platform (series này):

Mono-Repo (Turborepo):
├── apps/           (Shell + MFEs)
├── services/       (Microservices)
├── packages/       (shared-ui, shared-types, eslint-config)
└── infra/          (Terraform, K8s manifests)

Lý do:
- Nhiều shared code (UI, types, configs)
- Cross-cutting changes thường xuyên
- Lợi ích từ affected detection & remote caching
- Team size < 50 devs

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Summary

• Multi-Repo: clear ownership, simple CI, but sharing code is difficult
• Mono-Repo: easy to share code, atomic changes, needs tooling (Turborepo/Nx)
• Use Turborepo/Nx for affected detection + remote caching
• CODEOWNERS for code ownership in mono-repo

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Next article: Lesson 24: CI/CD Pipeline for Microservices & Micro Frontend