Monorepos: Building Your Software City in One LEGO Box

Introduction

Imagine you’re building a LEGO city. Would you rather have all your pieces—cars, buildings, roads, and trees—scattered across multiple boxes, or neatly organised in one big box? If you chose the big box, you already understand the core idea behind monorepos in software development.

In the world of software, projects are like LEGO cities. You have different components—backend (BE), frontend (FE), shared libraries, and tools—that need to work together seamlessly. Traditionally, teams store these components in separate repositories (like separate LEGO boxes). But as projects grow, managing these boxes becomes messy and inefficient.

History and Evolution

What is monorepos?

The idea of monorepos isn’t new. It started with tech giants like Google and Facebook, who were building massive software “cities.” They needed a way to manage millions of lines of code across hundreds of projects without losing their minds.

Think of it like this: if you’re building a LEGO city with thousands of pieces, having everything in one box makes it easier to find what you need and see how everything fits together. That’s exactly what monorepos do for code.

Evolution Over Time:

Monorepos have evolved over the years from being a niche practice to becoming a mainstream solution. Tools such as Nx, Turborepo, and Lerna have made monorepos more accessible, even for smaller teams. These tools are like LEGO sorting trays for developers, allowing them to organise and manage their code more efficiently.

Monorepos are now used by companies of all sizes, from startups to enterprises, to build everything from small apps to massive platforms.

Problem Statement

Let’s go back to the LEGO analogy. If you store your LEGO pieces in separate boxes—cars in one, buildings in another, roads in a third—you’ll face several challenges:

1. Missing Pieces: You might need a specific piece for both the cars and the buildings, but it’s only in one box.
2. Inconsistent Designs: If you update the roads, the cars might not fit anymore because they’re in a different box.
3. Hard to See the Big Picture: You can’t see how the cars, buildings, and roads look together until you open all the boxes.

In software, these challenges translate to:

• Code Duplication: Shared utilities or libraries must be copied across repos.
• Integration Issues: Changes in one repo (like BE) might break another (like FE).
• Complex Workflows: Developers must juggle multiple repos, increasing setup time and cognitive load.

Relevance to the Audience:

For developers and teams, these challenges mean slower development cycles, more bugs, and reduced productivity. Monorepos solve these problems by acting like one big LEGO box for your code.

Technology Overview

Basic Concepts:

A monorepo is like having one big LEGO box for your entire project. It contains:

• Frontend and backend code (cars and buildings)
• Shared libraries and utilities (common LEGO pieces)
• Configuration files and scripts (your building instructions)

Functionality:

Monorepos work by treating the entire codebase as a single unit. Tools like Nx and Turborepo act like LEGO sorting trays, helping you organise and manage your code more efficiently. For example:

• Shared Pieces: A utility function (like a LEGO wheel) can be used by both the BE and FE without duplication.
• Atomic Changes: You can update the roads and cars in one go, ensuring they fit together perfectly.
• Unified Workflow: You build and test the entire city at once, instead of working on each box separately.

Monorepos vs Multi-Repos

Let’s break down the advantages of using a monorepo (one big LEGO box) over multi-repos (separate boxes):

1. Easier to Share Pieces (Code Reusability)

• Multi-Repos: If you need a special LEGO piece for both the cars and the buildings, you have to dig through both boxes to find it.
• Monorepo: All the pieces are in one place, so you can easily grab what you need for any part of the city.
• In Code: Shared code (like utilities or libraries) can be used by both BE and FE without duplicating it or managing separate versions.

2. Everything Stays in Sync (Consistency)

• Multi-Repos: If you update the design of the roads, you might forget to update the cars to fit the new roads.
• Monorepo: You can see all the pieces at once, so you know the cars and roads will always work together.
• In Code: Changes in BE (like an API update) can be made alongside FE changes, ensuring everything works together without breaking.

3. Easier to Build and Test (Simpler Workflow)

• Multi-Repos: You have to open each box, build the cars, buildings, and roads separately, and then check if they fit together.
• Monorepo: You can build and test the whole city at once, making sure everything fits perfectly.
• In Code: You can run tests, build, and deploy the entire project (BE, FE, etc.) in one go, saving time and reducing errors.

4. One Place for Rules (Centralised Management)

• Multi-Repos: Each box might have its own instructions or rules, making it hard to keep track.
• Monorepo: You have one set of instructions for the whole city, so everyone follows the same rules.
• In Code: You can have one set of tools, configurations, and standards for the entire project, making it easier for teams to collaborate.

5. Easier to See the Big Picture (Visibility)

• Multi-Repos: You can’t see how the cars, buildings, and roads look together until you open all the boxes.
• Monorepo: You can see the whole city as you build it, making it easier to spot problems or improvements.
• In Code: Developers can see how changes in one part (like BE) affect another (like FE), improving collaboration and decision-making.

6. Simpler for New Builders (Onboarding)

• Multi-Repos: A new builder has to learn where each box is and how to use them separately.
• Monorepo: Everything is in one place, so it’s easier for new builders to get started.
• In Code: New developers only need to clone one repository and understand one setup, making onboarding faster.

Disadvantages of Monorepos

While monorepos have many advantages, they’re not without their challenges. Let’s explore the downsides:

1. Scalability Issues

• Problem: A big LEGO box can get messy if you don’t organise it properly. Similarly, large monorepos can become slow and unwieldy.
• In Code: As the codebase grows, build times and tooling performance can degrade without proper optimisation.

2. Learning Curve

• Problem: Switching to a monorepo requires learning new tools and workflows, like figuring out how to use a new LEGO sorting tray.
• In Code: Developers need to learn tools like Nx, Bazel, or Turborepo, which can take time.

3. Tooling Dependency

• Problem: Monorepos rely heavily on tools to manage builds, dependencies, and workflows. If the tools aren’t well-maintained, it can cause issues.
• In Code: Teams are locked into specific tools, which may not always meet their needs.

4. Complexity for Small Projects

• Problem: If you’re building a small LEGO set, a big box might be overkill. Similarly, monorepos can add unnecessary complexity for small projects.
• In Code: For small teams or simple projects, a monorepo might introduce more overhead than benefits.

5. Versioning Challenges

• Problem: In a monorepo, all code shares the same version, which can make it harder to manage independent releases.
• In Code: If one part of the codebase needs to be updated, it might force updates across the entire project.

Potential Solutions:

Emerging trends like distributed builds and incremental tooling are addressing scalability issues. Additionally, better documentation and community support are making monorepos more accessible.

Practical Applications

Real-World Use Cases:

Google: Think of their approach like building an enormous LEGO city. They use a monorepo to manage billions of lines of code, making it easier to piece everything together seamlessly.

Microsoft: They’ve jumped on the monorepo trend with projects like TypeScript and Visual Studio Code. This shift has really boosted collaboration across their teams, allowing for smoother workflows and better communication.

Startups: Many startups are embracing monorepos too! By keeping their entire tech stack—front end, back end, and mobile under one roof, they’re cutting down on complexity and speeding up their development process.

Impact Analysis:

Monorepos have revolutionised how teams collaborate and ship software. They enable faster iteration, better code reuse, and improved visibility across projects—just like building a LEGO city in one big box.

Challenges and Limitations

Current Challenges:

1. Scalability: A big LEGO box can get messy if you don’t organize it properly. Similarly, large monorepos can become slow and unwieldy without the right tools.
2. Learning Curve: Switching to a monorepo requires learning new tools and workflows, like figuring out how to use a new LEGO sorting tray.
3. Tooling Dependency: Monorepos rely heavily on tools like Nx or Bazel, which can add complexity.

Future Outlook

Emerging Trends:

1. AI-Powered Tooling: Tools that use AI to optimise builds and dependency management, like a smart LEGO sorter.
2. Hybrid Repos: Combining the best of monorepos and multi-repos for specific use cases, like having a big box for your city and smaller boxes for special sets.
3. Cloud-Native Monorepos: Integrating monorepos with cloud platforms for seamless deployment.

Predicted Impact:

As software projects grow in complexity, monorepos will become even more critical. They’ll enable teams to build faster, collaborate better, and deliver higher-quality software—just like building the ultimate LEGO city.

Conclusion

Monorepos are like having one big LEGO box for your software projects. They centralize your code, simplify workflows, and enable better collaboration, making them a powerful tool for modern development. While they’re not without challenges, the benefits often outweigh the drawbacks, especially for large or interconnected projects.