Monorepo Build Processes: Makefiles or Modern Build Tools?

The Importance of Build Processes in Monorepos

Monorepo structures house multiple projects within a single version control repository. This approach can facilitate code sharing, simplify dependency management, and improve the overall development experience. However, as the number and size of projects grow, build processes become complex, and performance issues can arise. Especially in large monorepos, rebuilding all projects from scratch every time leads to unnecessary time loss and resource waste. At this point, choosing an efficient build system becomes critical.

In this post, I will delve into two main build approaches for monorepos: traditional Makefiles and more modern build tools. I will discuss which is more suitable in which scenario, their trade-offs, and provide concrete examples from my real-world experiences. My aim is to help you make the right decision for your own projects.

The Traditional Approach: Makefiles and Their Depths

Makefiles have been a standard tool in the software development world for many years. Thanks to their simple syntax and flexible structure, they are used for various build and automation tasks. In monorepos, it's possible to manage basic build processes by creating separate Makefiles for each project or subdirectory. The biggest advantage of this approach is that it's available by default on most systems and has a relatively low learning curve.

However, Makefiles have some serious limitations for monorepos. Firstly, dependency management needs to be done manually. You must explicitly specify which file depends on which rule and in what order it should be built. In a large monorepo, keeping these dependencies accurate and up-to-date is extremely difficult. For example, when you make a code change, you need to manually identify all affected files and all other build steps that use those files. This situation can lead to complexity known as "dependency hell."

Another significant issue is scalability. While Makefiles generally support parallel builds, optimizing and making them efficient is difficult. Especially as the number of projects in a monorepo increases, it becomes challenging for Make to manage the workflow and prevent unnecessary builds. In one project of my own, just a few lines of code change caused the entire project to rebuild, taking 45 minutes. This incredibly slows down the development cycle.

# A sample Makefile snippet
SRC = main.c utils.c
OBJ = $(SRC:.c=.o)
CC = gcc
CFLAGS = -Wall -g
LDFLAGS =

all: myprogram

myprogram: $(OBJ)
    $(CC) $(LDFLAGS) $(OBJ) -o myprogram

%.o: %.c
    $(CC) $(CFLAGS) -c $< -o $@

clean:
    rm -f $(OBJ) myprogram

This simple example shows how Make works. However, imagine hundreds of such files in a monorepo. Tracking dependencies becomes a nightmare.

Limitations of Makefiles and Real-World Scenarios

In real-world scenarios, managing monorepos with Makefiles often becomes unsustainable. Especially as the number of projects increases, correctly establishing and managing the logic for "incremental build" becomes very complex. A small change in one project can trigger unexpected dependencies in other projects. This wastes developer time and reduces the reliability of build processes.

At one point, in a large enterprise software project, we used Makefiles to manage the build processes of different modules. As the project grew, a make clean all command would take a full day. This situation also severely impacted the performance of CI/CD pipelines. Waiting that long for every deploy was unacceptable. Moreover, we had to write a separate script to track dependencies between Makefiles. This script itself was complex and error-prone. As a result, build times became a major headache for both developers and the operations team.

⚠️ Makefile Scalability Issues

Makefiles are a great tool for small and medium-sized projects. However, in monorepos with hundreds or thousands of modules, manually tracking dependency management and optimizing build processes is extremely difficult. This slows down development speed and increases operational costs.

Furthermore, the debugging capabilities of Makefiles are also limited. When you encounter a build error, it can be difficult to find exactly where and why it occurred. Error messages are often vague, and you may need to perform very in-depth analysis to understand which dependency was triggered. This makes the learning process even more difficult, especially for new team members.

Modern Build Tools: NX, Bazel, and Others

Many modern build tools have been developed to overcome the limitations of traditional Makefiles. These tools generally offer more advanced features and are optimized for large-scale monorepos. Prominent among these tools are NX and Turborepo, popular in the JavaScript ecosystem. Additionally, more general-purpose and powerful tools like Bazel are also available.

The biggest advantage of these modern tools is their intelligent dependency tracking and caching mechanisms. When you make a code change, they identify only the projects and dependencies affected by that change. Then, they rebuild only the affected parts. If a project's build has already been done and its code hasn't changed, that build result is retrieved from the cache, and the build time is significantly reduced. For example, in a project I worked on using NX, I managed to reduce the build time, which previously took 1 hour, to just 5-10 minutes by building only the affected modules. This creates a revolutionary difference in development efficiency.

// nx.json - Example NX configuration
{
  "npmScope": "myorg",
  "affected": {
    "defaultBase": "main"
  },
  "tasksRunnerOptions": {
    "default": {
      "runner": "nx/tasks-runners/default",
      "options": {
        "cacheableOperations": ["build", "lint", "test", "e2e"],
        "parallel": 3,
        "useDaemonProcess": true
      }
    }
  },
  "targetDefaults": {
    "build": {
      "dependsOn": ["^build"],
      "outputs": ["{options.outputPath}"]
    },
    "lint": {
      "outputs": ["{options.outputFile}"]
    }
  }
}

This nx.json file gives an idea of how NX works. Fields like cacheableOperations and dependsOn form the basis for intelligent dependency tracking and caching.

These tools can also offer distributed build capabilities to make builds more efficient. For instance, Bazel's remote caching and execution features help further reduce build times in large-scale teams. This allows CI/CD pipelines to run faster and enables developers to get feedback more quickly. In a client project, we reduced CI build times by 70% using Bazel's distributed build feature.

Advantages and Disadvantages of Modern Tools

One of the most significant advantages offered by modern build tools is the improvement in developer experience. Fast build times, automatic dependency management, and better debugging capabilities allow developers to work more efficiently. For example, commands like NX's nx affected:build allow you to build only the changed projects. By using this command in a CI/CD pipeline, you can eliminate unnecessary builds.

Another major advantage is that these tools generally have better documentation and community support. Tools like NX and Turborepo are widely used, especially in JavaScript and TypeScript-based projects, and have a strong community in this ecosystem. This allows you to easily find solutions for the problems you encounter.

However, these modern tools also have some disadvantages. Their learning curves are generally higher than Makefiles. Especially more complex tools like Bazel require a significant learning process. Their setup and configurations can also be more cumbersome compared to Makefiles. For example, setting up and integrating Bazel into your project might require a day's work.

Furthermore, these tools are often more suited to a specific language or ecosystem. While NX and Turborepo primarily focus on the JavaScript/TypeScript ecosystem, Bazel is more general-purpose but can increase complexity. If you use different languages and technologies in your project, you need to carefully evaluate the compatibility and integration of these tools. In one project, we tried to manage build processes for both Node.js and Go services with NX. We struggled a bit at first, but we managed it through custom tasks and plugins.

ℹ️ Fast Feedback from Modern Tools

Modern build tools dramatically reduce build times through intelligent dependency tracking and caching. This provides faster feedback to developers and increases overall productivity. Especially in large monorepos, this difference is palpable.

Trade-off Analysis: Which Case for Which?

The choice between Makefiles and modern build tools depends on your project's scale, complexity, and your team's experience. For small and simple monorepos, Makefiles might still suffice. If your project has only a few modules and the dependencies are not complex, starting with Makefiles might be logical. In this case, the learning cost will be low, and you can quickly get a solution.

However, as your project grows and the number of modules increases, the limitations of Makefiles will become more apparent. At this point, migrating to a modern build tool like NX, Turborepo, or Bazel becomes inevitable. Modern tools will be more suitable, especially in the following situations:

• Large-scale monorepos: Intelligent dependency tracking and caching are critical in projects with hundreds or thousands of modules.
• Need for fast development cycles: Situations where developers need to get fast feedback and deployment processes need to be accelerated.
• Complex dependencies: Projects where complex dependencies exist between different modules, making manual management difficult.
• CI/CD automation: Situations where build processes need to be integrated into CI/CD pipelines and automated.

For example, let's consider managing the backend services of an e-commerce platform in a single monorepo. This platform has dozens of microservices, shared libraries, and different technologies. In this structure, instead of building the entire system with every service change, building only the affected services and their dependencies can reduce build times from hours to minutes. A command like NX's nx affected:build --parallel=5 can be a lifesaver in this scenario.

💡 Choosing the Right Tool is Important

Choosing the right build tool for your monorepo is critical for your project's future success. Consider your project's scale, complexity, and your team's competencies to select the most suitable tool. While Makefiles are suitable for a quick start, modern tools are generally a better investment for scalability.

It's important to remember that every tool has its own trade-offs. Makefiles are simple but not scalable. Modern tools are powerful but harder to learn. The key is to find the best balance that suits your project's current and future needs. Sometimes, a hybrid approach might also be considered; for example, managing the general monorepo structure with a modern tool while using custom Makefiles for specific sub-projects. However, this usually adds complexity and requires careful planning.

Real-World Applications and Performance Metrics

Performance in monorepo build processes is one of the most critical factors directly affecting development speed. Some performance metrics I've obtained in real-world scenarios clearly demonstrate the difference between these tools.

In a monorepo project where we managed the backend services of a production ERP system, we initially used Makefiles. This system had approximately 200 dependent services and libraries. The make clean all command took an average of 2 hours in the CI environment. This was unacceptable for frequent tests and deployments.

To solve this problem, we migrated to NX. Thanks to NX's intelligent dependency graph and caching feature, we managed to reduce build times in the same CI environment to an average of 15-20 minutes. This meant an improvement of almost 90%. This improvement not only reduced build times but also allowed developers to iterate faster and catch errors earlier.

# Example of building affected projects with NX
nx affected:build --parallel=5 --base=main --head=HEAD

The command above builds only the projects that have changed since the main branch, using 5 parallel processes. This completely eliminates unnecessary builds.

In another scenario, we used Bazel in a monorepo for a mobile app team. This project included both iOS and Android native code, React Native, and shared TypeScript libraries. Thanks to the custom rules Bazel provides for each language and technology, we managed to handle a very complex build process. Using Bazel's distributed build feature (remote execution), we reduced CI build times from 3 hours to 45 minutes. This significantly accelerated the team's weekly deployment cycle.

🔥 Performance Metrics Are Crucial

Performance in monorepo build processes is critical for developer productivity and operational costs. Concrete metrics obtained (build times, disk usage, CPU usage) show how valuable it is to choose and optimize the right tool. Reducing a 1-hour build time to 10 minutes is not just a time saving, but also a great gain for developer motivation.

These experiences clearly show how effective modern build tools can be in large-scale monorepos. While Makefiles are still valid for simple projects, they are often insufficient for complex and growing monorepos. Choosing the right tool and optimizing build processes play a critical role in the success of your projects.

Conclusion: A Pragmatic Decision-Making Process

When it comes to monorepo build processes, a "one-size-fits-all" approach is not applicable. When choosing between Makefiles and modern build tools, you need to consider your project's specific needs and your team's capabilities. For small and simple projects, Makefiles can offer a quick and easy starting point. However, as your project grows and its complexity increases, the scalability and performance advantages offered by modern tools like NX, Turborepo, or Bazel will become more apparent.

Based on my own experiences, if you are working on a monorepo and build times are starting to become a problem, investing in a modern build tool is definitely worthwhile. NX and Turborepo are strong options, especially in the JavaScript/TypeScript ecosystem. For more general-purpose and complex scenarios, Bazel is an excellent solution. These tools not only reduce build times but also simplify dependency management and significantly improve the developer experience.

It's important to remember that even the best tool will not perform as expected if it's not configured correctly. Therefore, it's important to optimize the tool you choose according to your project's needs and to regularly review your build processes. Monitoring build times, adjusting caching strategies, and optimizing parallel processing options are critical steps for continuous improvement.

In conclusion, starting with Makefiles can provide an advantage, especially for inexperienced teams. However, in line with long-term scalability and performance goals, the possibilities offered by modern build tools should not be overlooked. A pragmatic decision-making process will allow you to choose the most suitable tool by considering your project's current situation and future growth potential.