Monorepos Simplified with Nx

The monorepo itself was never the hard part. Putting all your projects in one repository is trivial. The hard part is everything that happens next: builds that get slower every month, a CI pipeline that rebuilds the entire world for a one-line change, and architectural boundaries that exist only in a wiki nobody reads. Without tooling, a monorepo is just a big folder quietly rotting from the inside.

That’s the gap Nx fills. It doesn’t just store your code together, it understands how the pieces relate, and uses that understanding to keep a large codebase fast and disciplined as it grows. Let’s break down what actually makes it work.

Everything starts with the project graph

The single idea behind Nx is that your repository is a graph: a set of projects (apps and libraries) connected by their dependencies. Nx builds that graph by reading your imports, and almost every powerful feature flows from it. You can even visualize it:

nx graph

Once a tool genuinely understands which project depends on which, it can stop treating your repo as one undifferentiated blob and start making smart, surgical decisions.

Only build and test what actually changed

This is the feature that pays for the whole setup. Instead of rebuilding everything on every commit, Nx looks at what you changed, walks the graph to find every project affected by that change, and runs tasks only for those:

# Lint, test, and build only the projects impacted by this branch
nx affected -t lint test build --base=main

On a small repo that’s a nice-to-have. On a large one, it’s the difference between a CI run that takes twenty minutes and one that takes three. Touch a leaf library, and the apps that don’t depend on it are simply skipped.

Stop doing the same work twice

Nx caches the result of every task against a hash of its inputs, source files, dependencies, environment, and config. If nothing relevant changed, it replays the stored output instantly instead of recomputing it:

// nx.json
{
  "targetDefaults": {
    "build": { "cache": true, "dependsOn": ["^build"] },
    "test":  { "cache": true },
    "lint":  { "cache": true }
  }
}

The real multiplier arrives when you move that cache off the local machine. With remote caching, the result one developer (or one CI job) computed is reused by everyone else, so the same build never runs twice across the whole team. A green pipeline that finishes in seconds because every input was already seen is a genuinely different way to work.

Enforce your architecture instead of hoping for it

Most “architecture” lives in documentation and dies in code review. Nx lets you encode the rules and have the linter enforce them. You tag each project by scope and type:

// libs/orders/data-access/project.json
{ "tags": ["scope:orders", "type:data-access"] }

Then you declare which tags are allowed to depend on which, and a violation becomes a failing lint check, not a debate:

"@nx/enforce-module-boundaries": ["error", {
  "depConstraints": [
    { "sourceTag": "scope:orders", "onlyDependOnLibsWithTags": ["scope:orders", "scope:shared"] },
    { "sourceTag": "type:feature", "onlyDependOnLibsWithTags": ["type:data-access", "type:ui", "type:util"] }
  ]
}]

Now a feature library physically cannot import another team’s internals, and your clean architecture stays clean because the tooling refuses to let it rot. This is the part that keeps a big repo from collapsing into spaghetti as more people touch it.

Generators keep the repo from drifting

When twenty developers create libraries by hand, you get twenty subtly different structures. Generators fix that by scaffolding new projects in one consistent shape:

nx g @nx/react:lib ui-buttons --directory=libs/shared/ui

Consistency isn’t cosmetic here. A predictable structure is what makes the graph, the boundaries, and the caching all work reliably.

Best practices that keep it scaling

• Think library-first:

Keep apps thin and push real logic into well-scoped libraries. The more your code lives in tagged libs, the more leverage you get from affected commands and boundaries.

• Tag everything from day one:

A scope: and a type: on every project is what turns the boundary rules from theory into enforcement. Retrofitting tags later is painful, so do it up front.

• Always enable remote caching in CI:

Local caching helps one person; remote caching helps the whole team and your pipeline. It’s the highest-leverage switch you can flip.

• Keep the graph acyclic:

Circular dependencies break caching assumptions and signal a design smell. Run the graph view regularly and untangle cycles before they spread.

Wrapping up

Nx doesn’t make monorepos magic, it makes them manageable. The project graph gives the tooling real understanding of your code, affected commands and caching keep it fast no matter how big it grows, and tag-based boundaries keep the architecture honest under pressure from many contributors.

A monorepo is only “simplified” when the tooling does the coordination for you. Set up the graph, lean on affected and caching, enforce your boundaries in lint, and a repo with dozens of projects can feel as snappy and predictable as a small one. That’s the whole point.