As frontend applications scale, managing multiple projects with shared UI components becomes challenging. Different teams may end up duplicating components, leading to inconsistency and increased maintenance effort.
This is where a monorepo combined with a reusable component library becomes powerful.

In this document, we will cover:

• What a Monorepo is
• Why we use pnpm for monorepo management
• How to build a reusable component library
• How multiple applications consume shared components

What is a Monorepo?

 A Monorepo (monolithic repository) is a single repository that contains multiple applications and shared packages.

Instead of maintaining separate repositories like this:

• app-1
• app-2
• ui-library

We organize everything in one place:

project-root

├ apps

│  ├ app-1

│  ├ app-2

├ packages
│  ├ ui
│  ├ utils

This structure allows all applications to share code efficiently.

Why Use pnpm for Monorepo?

• pnpm is a fast and efficient package manager that is well-suited for monorepos. 
• pnpm uses a global store and links dependencies, reducing duplication.
• Dependencies are installed once and reused across projects. 
• pnpm provides built-in support for managing multiple packages in a monorepo.
• All applications use the same versions of shared dependencies.

Why pnpm Instead of npm or Yarn?

pnpm provides several advantages for monorepo management:

– Faster dependency installation

– Reduced disk space usage through shared dependency storage

– Strict dependency resolution

– Better workspace management

– Improved performance for large-scale projects

Compared to traditional package managers, pnpm is optimized for handling multiple applications and shared packages efficiently.

Why Build a Reusable Component Library?

  In large applications, UI duplication is common:

• Buttons created multiple times
• Forms implemented differently
• Inconsistent styling

A shared component library solves this.

Benefits:

Reusability:
Write once, use across multiple applications

Consistency
Unified design system across apps.

Maintainability
Fix or update a component in one place.

Faster development
Developers can reuse ready-made components.


Real-World Scenario

  Imagine a company with multiple frontend applications:

– Customer Portal

– Admin Dashboard

– Internal CRM

All applications require common UI elements such as:

– Buttons

– Input fields

– Modals

– Typography

– Theme configuration

Without a shared component library, teams often duplicate the same components across projects. Over time, this leads to:

– Inconsistent UI behavior

– Repeated development effort

– Difficult maintenance

– Styling mismatches

With a monorepo and shared UI package, components are maintained in one place and consumed across all applications, ensuring consistency and faster development.

Monorepo Architecture

A typical structure looks like this:

Project-root/

├── apps/

│   ├── app-1/           

│   ├── app-2/       

│   └── app-3/    

├── packages/

│   └── ui/              # Shared UI components 

├── package.json         # Root package with shared devDependencies

├── pnpm-workspace.yaml  # Workspace configuration

├── tsconfig.base.json   # Shared TypeScript config

├── eslint.config.js     # Shared ESLint config

└── .env.example         # Environment template

• Applications consume components from the ui package
• Shared logic and styles live inside packages
• All applications and shared packages are versioned together.

Setting up Monorepo with pnpm

Step 1: Initialize Project

Create a root project:

mkdir monorepo
cd monorepo
pnpm init

Step 2: Enable Workspaces

Create a pnpm-workspace.yaml file:

packages:

  – apps/*
  – packages/*

Step 3: Create Applications and Packages

apps/

  app-1

  app-2

packages/

  ui

Step 4: Create a UI Component

Inside packages/ui:

Example:

export const Button = ({ label }) => {

  return <button>{label}</button>

}

Step 5: Use Component in Apps

Inside an application:

import { Button } from “@project/ui”

<Button label=”Click Me” />

Now the same component is shared across multiple apps.

Challenges and Tradeoffs

While monorepos provide many advantages, they also introduce certain challenges.

1.Initial Setup Complexity

Setting up workspace management, shared tooling, TypeScript configurations, and linting requires additional effort during the initial stages.

2.Build Performance

As the repository grows, build times and CI/CD pipelines may become slower without proper caching and incremental builds.

3.Dependency Conflicts

Different applications may require different dependency versions, which can sometimes create compatibility issues.

4.Team Coordination

Since multiple applications live inside the same repository, teams must coordinate changes carefully to avoid breaking shared packages.

5. Learning Curve

Developers unfamiliar with monorepo architecture may initially find the structure and workflows difficult to understand.

Despite these tradeoffs, monorepos are highly effective for teams managing multiple related applications and shared systems.

Benefits of This Approach

• Code reusability across multiple applications
• Centralized UI management
• Faster development cycles
• Reduced duplication and bugs
• Scalable architecture for growing applications

Using a Monorepo with pnpm to build a reusable component library helps streamline frontend development.

It allows teams to:

• Share components efficiently
• Maintain consistency
• Scale applications with ease

This approach is especially useful in projects with multiple applications that require a unified design system and shared functionality.