Choosing Monorepo or Polyrepo depends on project relevance, team structure and maintenance capabilities; 2. If multiple projects share code, frequently cross-project modifications, and team collaboration is closely linked, Monorepo is more efficient and can be managed by Nx or Turborepo; 3. If the project is independent, the technology stack is different, or permission isolation is required, Polyrepo is simpler and safer; 4. A compromise solution for progressive Monorepo or unified configuration templates can be adopted; 5. The structure selection should match the current stage requirements, and there is no absolute advantage or disadvantage. The best solution is the best solution.

When you start planning a medium- and large-scale front-end project, or the team gradually expands, the structural problem of the code base will sooner or later emerge: Should you use Monorepo (single warehouse) or Polyrepo (multi-warehouse)?

There is no absolutely correct answer to this question, but choices can profoundly affect development efficiency, collaboration methods, release processes and long-term maintenance costs. The following is to break down the differences between the two from several key dimensions to help you make decisions that are more suitable for the current situation of the team.

1. What are Monorepo and Polyrepo?

• Monorepo (monopo warehouse) : All projects, modules, and services are placed in a code warehouse. For example, a warehouse contains official website, management background, component library, tool functions, etc.
• Polyrepo (multiple warehouse) : Each project or module is independent as a warehouse. There is a repo on the official website, a repo on the component library, and another repo on the background system.

It sounds simple, but behind it is the philosophical differences in how organizations are, dependency management, and teamwork.

2. Monorepo's advantages and applicable scenarios

? Suitable for these situations:

• Multiple projects are highly relevant : For example, you have multiple front-end applications sharing the same set of UI components, tool functions, or configuration.
• Frequent cross-project modifications : One need to modify the component library and two applications at the same time. Monorepo can submit it at one time to avoid chain waiting for "distribution → update dependency → verification".
• Unified technology stack and specifications : it is easier to unify ESLint, TypeScript configuration, build scripts, etc.
• Shared code is safer : internal packages do not need to be published to npm, and they are directly referenced locally to avoid version confusion or private package management issues.

? Common tool support:

• Nx : Powerful task scheduling and dependency analysis, suitable for mixed projects such as Angular, React, and Vue.
• Turborepo : lightweight, fast, based on file hash cache, suitable for the modern JS ecosystem.
• Lerna : An old tool suitable for publishing multiple npm packages, but is now gradually replaced by Turborepo.

For example: you upgraded the Button of the component library and needed to adjust the usage in three applications. In Monorepo, you can modify all codes at once, run CI together, and find out immediately if there is any problem. In Polyrepo, you have to send the component library first and then update the project one by one, which is prone to missed or inconsistent versions.

3. Polyrepo's advantages and applicable scenarios

? Suitable for these situations:

• The project is completely independent : for example, the company has an e-commerce front desk, an internal HR system, and a data platform, which has nothing to do with each other and the team is different.
• The need for permission isolation is strong : Some projects involve sensitive data and require strict access control. They do not want everyone to clone the entire code base.
• The technology stack is very different : different frameworks and construction methods are used for different projects, and forcibly merged increases complexity.
• Small teams or startups : fewer initial projects, more simple and direct independent warehouses, and there is no need to introduce Monorepo toolchain.

?? Potential problems:

• Repeated configuration : Each repository must maintain its own lint, test, and CI scripts, which are prone to inconsistencies.
• Dependency update trouble : After the shared library is updated, multiple repositories need to be updated manually or through tools such as Dependabot.
• Cross-project collaboration is expensive : Fixing an underlying bug, it may require submitting multiple PRs and publishing multiple versions.

4. How to choose? The key is team and project relationship

Don't be biased by the "trend". Monorepo is very popular now, but not silver bullets. You can ask yourself a few questions:

• How many projects do you have? Do they share code?

  • Less than 3 and not shared? Polyrepo is simpler.
  • Multiple projects share components or tools? Monorepo is more efficient.

• Team size and collaboration?

  • Small teams are each responsible for independent products → Polyrepo.
  • Multiple people collaborate on developing the same ecosystem (such as designing multiple applications in the system) → Monorepo.

• Is there a capability to maintain complex toolchains?

  • Monorepo needs to invest in configuring Nx/Turborepo, CI cache, incremental construction, etc.
  • If the team has no manpower to do anything, it is safer to use Polyrepo first.

• Do you need fine permission control?

  • If the financial system and marketing page are completely unrelated, there will be security risks when putting them together.

5. Compromise solution: Progressive Monorepo

Don't have to choose one of two from the beginning. It can evolve like this:

1. Use Polyrepo first to keep it simple.
2. When two projects are found to be frequently dependent on each other, merge them into a Monorepo.
3. Use Turborepo or Nx management to gradually unify the configuration.
4. Sensitive projects remain in separate warehouses.

Alternatively, use the "multi-warehouse unified configuration template" method: use a config-repo to store ESLint, Prettier, and GitHub Actions templates, and synchronize to each project through scripts, taking into account independence and consistency.

Basically that's it. Monorepo is not “advanced”, nor is Polyrepo “l(fā)agged behind”. The key is to match your project coupling, team structure and maintenance capabilities.

If you have more and more front-end projects and more and more sharing code, Monorepo is worthy of serious consideration. But if the project is independent and the team is scattered, Polyrepo will be clearer and more controllable.

There is no optimal solution for the structure, only the choice that is most suitable for the current stage.

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