Nx Monorepos are a powerful way to enforce and operationalize backend architectural styles like Domain-Driven Design (DDD)
Instead of relying on conventions and documentation alone, Nx lets you codify those rules in the repo structure, build system, and linting layer—so architectural boundaries are enforced automatically.
DDD emphasizes clear boundaries between domains, explicit contracts, and controlled dependencies (for example, domain → application → infrastructure, but not the other way around). In a typical repository, these rules are easy to violate over time as the system grows and different teams contribute.
Nx provides three key capabilities that map neatly to DDD
variant="ordered"
items={[
{
title: "Project graph awareness",
content: [
"Nx models your repository as a graph of projects and their dependencies, which aligns with DDD's concept of bounded contexts and explicit relationships (see the project graph docs at nx.dev)."
]
},
{
title: "Task orchestration and caching",
content: [
"Nx runs builds, tests, and linting only where needed, with smart local and remote caching of task results."
]
},
{
title: "Enforceable boundaries",
content: [
"Via ESLint rules—especially `@nx/enforce-module-boundaries`—you can programmatically block imports that violate architectural rules."
]
}
]}
/>
Together, these features ensure that your DDD structure is not just recommended in diagrams, but actually enforced by the tooling during development and CI. Architectural drift becomes much harder because violations show up as lint errors or misconfigured dependencies rather than hidden design problems discovered much later.
For a backend using NestJS within an Nx workspace, you typically begin with a NestJS application under apps/ (for example, apps/api) and a set of libraries under libs/ representing your domains and cross-cutting concerns. Each domain is usually modeled as its own bounded context under libs, such as libs/orders/..., libs/payments/..., and libs/users/....
Within each domain, you split the code into sub-libraries that reflect DDD layers and patterns. A common structure for the orders domain might include:
items={[
{
content: [
"`libs/orders/domain` for entities, value objects, domain services, and domain events"
]
},
{
content: [
"`libs/orders/application` for use cases, application services, and ports"
]
},
{
content: [
"`libs/orders/infrastructure` for repositories, data mappers, and external integrations"
]
},
{
content: [
"`libs/orders/contracts` for DTOs, API contracts, and shared interfaces"
]
},
{
content: [
"`libs/orders/adapters` for driving or driven adapters such as REST controllers or message handlers"
]
}
]}
/>
Nx supports this style through its library generators and tagging system. Each library is a first-class project with its own configuration and targets. By modeling domains and layers as separate libraries, you obtain clearer ownership, better encapsulation, and more precise control over dependencies. This structure also lays the foundation for using Nx's project graph and lint rules to encode DDD boundaries directly into the workspace configuration.
Although a NestJS application in Nx generally uses Webpack under the hood—via the Nest CLI or Nx's Nest plugin—your libraries do not have to share that same bundler. You can keep the main NestJS application (for example, apps/api) on Webpack while configuring your domain libraries under libs/ to build with Vite.
This is possible because Nx allows each project—whether an app or a library—to define its own targets in its project.json, each using its own executor. One project might use the Nest executor that ultimately bundles with Webpack, while another uses a Vite-based executor or a simple TypeScript build. Nx orchestrates these heterogeneous build pipelines in a single workspace.
Nx's plugin and executor system, documented at nx.dev, is what enables this mixed-tooling approach. The key is that the application and its libraries form a graph of buildable units, each with its own optimized configuration, rather than a monolithic build pipeline tied to a single tool.
A central technique for both effective DDD and extracting maximum value from Nx is to use fine-grained libraries rather than a few large ones. Instead of a single libs/orders package, you split it into multiple libraries like libs/orders/domain, libs/orders/contracts, libs/orders/application, libs/orders/adapters-rest, and libs/orders/adapters-messaging.
Each of these libraries becomes its own project in the Nx project graph. It has independent build, test, and lint targets, and its own dependency rules. For example, domain should not import from infrastructure or adapters; application may depend on domain but not vice versa. This structure enables strict layering while also allowing fine-grained control over what depends on what.
The payoff is that Nx can now take advantage of this granularity for performance. This means that even as the codebase grows large, the cost of each change remains proportional to the actual impact area rather than the size of the entire system.
Nx significantly improves backend performance and feedback loops through caching and incremental execution.
First, there is local computation caching: when you run a task such as nx test orders-domain or nx lint orders-contracts, Nx records the inputs (source files, environment, command arguments) and the produced outputs. If you run the same task again with unchanged inputs, Nx replays the cached result instantly instead of recomputing it.
Second, Nx supports incremental builds and tests via its "affected" commands. When you invoke nx affected:test or nx affected:build, Nx analyzes the changes in your workspace and determines which projects—based on the project graph—are impacted. Only those projects and their dependents are rebuilt or retested. Modifying libs/users/domain will not trigger work for unrelated domains like libs/payments.
Third, Nx provides remote caching and CI sharing through Nx Cloud or compatible distributed cache solutions. Cache artifacts produced in CI can be reused by developers locally, and vice versa, as long as inputs match. This can drastically reduce CI times and makes local verification nearly instantaneous when work has already been validated in another environment.
Enforcing DDD Boundaries in an Nx Workspace
Enforcing DDD boundaries in an Nx workspace is achieved primarily through ESLint and the @nx/enforce-module-boundaries rule. Each library in the workspace can be annotated with tags in its configuration, typically indicating its domain scope and architectural layer.
For example, the orders-domain library might have tags like ['scope:orders', 'layer:domain'], while orders-application uses ['scope:orders', 'layer:application'], and orders-infrastructure is tagged ['scope:orders', 'layer:infrastructure'].
Configuring Dependency Rules
In the workspace ESLint configuration—often eslint.config.mjs or .eslintrc.json—you then define rules describing which tags may depend on which.
Typical DDD-inspired rules include
items={[
{
content: ["Libraries with `layer:domain` should not depend on any infrastructure or application code"]
},
{
content: ["`layer:application` may depend on `layer:domain`"]
},
{
content: ["`layer:infrastructure` may depend on both domain and application"]
},
{
content: ["Cross-scope imports (for instance, from `scope:orders` to `scope:payments`) are limited or disallowed"]
}
]}
/>
Enforcement in Practice
When a developer introduces an import that violates these dependency rules, ESLint surfaces an error immediately, often with a clear explanation of which constraint was broken.
Over time, this prevents architecture drift and keeps DDD boundaries intact as the codebase evolves.
NestJS Integration with Nx
NestJS integrates smoothly with Nx, and Nx provides first-class support and generators for Nest-based backends. In a typical arrangement, apps/api is your NestJS application containing the entry point and main module, while the actual domain and application logic resides in libraries under libs/. The application imports its providers, modules, and controllers from these DDD-oriented libraries.
In this model, Nest itself often uses Webpack for building the final application bundle, while the supporting libraries are compiled with Vite or plain TypeScript via Nx executors. Nx coordinates these tools so that the Nest application compiles quickly, leveraging pre-built and cached outputs from the libraries. As a result, most heavy compilation work is done once at the library level and reused across runs.
From an architectural perspective, the Nest app in apps/api should depend only on higher-level libraries such as orders-adapters-rest or orders-application, not directly on low-level infrastructure details. The combination of Nx tags and ESLint rules enforces this layering.
Combining Nx with Domain-Driven Design
Combining Nx with Domain-Driven Design for a backend—especially one built with NestJS—yields several tangible benefits. You get explicit domain modeling by organizing code into libraries per domain and per layer, mirroring bounded contexts and clear responsibilities. Performance is improved by using fast tooling like Vite for libraries and leveraging Nx's local and remote caching so repeated tasks are effectively free.
Incremental and distributed continuous integration becomes practical through Nx's affected commands and support for Nx Cloud or other remote caches. Only changed or affected parts of the system are built and tested, allowing large monorepos to maintain rapid feedback loops. Architectural boundaries are encoded and enforced via @nx/enforce-module-boundaries and the tagging system, turning DDD rules into machine-checked constraints instead of informal guidelines.
As a result, DDD ceases to be just a conceptual model or a set of diagrams in documentation. This alignment between design and tooling is what makes Nx particularly effective for large, evolving backends built along DDD principles.
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