Best Practices for Angular Architecture

Angular is a robust, component-based framework that encourages modularity, scalability, and maintainability. However, as applications grow, improper architecture can lead to spaghetti code, poor maintainability, and performance issues.

Following Angular architecture best practices ensures that applications remain scalable, testable, and easy to manage, especially in large teams or enterprise projects.

In this comprehensive guide, we will cover:

Guidelines for creating modular and maintainable Angular applications
When to create new feature modules vs using shared modules
How to structure services, components, and modules for scalability
Examples of practical folder structure and modular design
Performance considerations and maintainable code patterns

1. Modular Design in Angular

A modular design breaks an application into self-contained, reusable units, each responsible for a specific feature or functionality. Angular supports modular design using NgModules.

Benefits of Modular Design

Reusability – Modules or components can be reused across multiple features or projects.
Maintainability – Smaller, self-contained units are easier to maintain and debug.
Scalability – New features can be added without disrupting existing modules.
Team Collaboration – Different teams can work on different modules independently.

Example of a Modular Angular App

src/app/
 ├─ core/                   # Core services and singleton providers
 │   ├─ core.module.ts
 │   └─ services/
 ├─ shared/                 # Shared components, directives, pipes
 │   ├─ shared.module.ts
 │   └─ components/
 ├─ features/               # Feature modules
 │   ├─ user/               # UserModule
 │   ├─ product/            # ProductModule
 │   └─ order/              # OrderModule
 ├─ app-routing.module.ts   # Application routing
 └─ app.module.ts           # Root module

CoreModule: Singleton services like authentication, logging
SharedModule: Reusable UI components like buttons, modals
Feature Modules: Domain-specific functionality

2. Guidelines for Creating Modular and Maintainable Applications

a) Keep Root Module Lean

The AppModule should only include:

The root component (AppComponent)
Root-level services
Global modules like BrowserModule and AppRoutingModule

Avoid cluttering AppModule with feature-specific components.

@NgModule({
  declarations: [AppComponent],
  imports: [
BrowserModule,
AppRoutingModule,
CoreModule,
SharedModule  ],
  bootstrap: [AppComponent]
})
export class AppModule {}

b) Use Feature Modules for Each Domain

Group related functionality in feature modules:

@NgModule({
  declarations: [UserListComponent, UserDetailComponent],
  imports: [CommonModule, UserRoutingModule]
})
export class UserModule {}

Keeps related components, services, and routing together
Makes lazy loading easier

c) Shared Module for Reusable Components

SharedModule contains components, directives, and pipes that are used across multiple modules:

@NgModule({
  declarations: [ButtonComponent, HighlightDirective, FormatDatePipe],
  imports: [CommonModule],
  exports: [ButtonComponent, HighlightDirective, FormatDatePipe]
})
export class SharedModule {}

Components declared here can be imported into feature modules
Avoid declaring services here unless stateless

d) Core Module for Singleton Services

CoreModule contains services that should only have a single instance across the application:

@NgModule({
  providers: [AuthService, LoggerService]
})
export class CoreModule {
  constructor(@Optional() @SkipSelf() parentModule: CoreModule) {
if (parentModule) {
  throw new Error('CoreModule is already loaded. Import only in AppModule.');
}  }
}

Prevents multiple instances of core services
Ensures singleton services for authentication, logging, etc.

e) Use Lazy Loading for Feature Modules

Lazy loading improves performance by loading modules only when needed:

const routes: Routes = [
  { path: 'users', loadChildren: () => import('./features/user/user.module').then(m => m.UserModule) }
];

Only loads UserModule when user navigates to /users
Reduces initial bundle size

3. When to Create New Feature Modules vs Using Shared Modules

a) Feature Module

Create a feature module when:

Functionality is domain-specific
Components/services are closely related
You want to enable lazy loading

Example: UserModule containing UserListComponent, UserDetailComponent, UserService.

b) Shared Module

Create a shared module when:

Functionality is generic and reusable
Components/services are used in multiple feature modules
Avoids code duplication

Example: SharedModule containing ButtonComponent, HighlightDirective, DatePipe.

c) Core Module

Create a core module when:

Services should be singleton
App-wide providers like authentication, logging, HTTP interceptors are needed
Only imported in AppModule

4. Structuring Services for Scalability

a) Use Dependency Injection

Angular services provide reusable business logic and can be injected into components or other services:

@Injectable({
  providedIn: 'root'
})
export class UserService {
  constructor(private http: HttpClient) {}

  getUsers() {
return this.http.get('/api/users');  }
}

providedIn: 'root' ensures singleton service
Keeps business logic separate from UI components

b) Organize Services by Feature

features/user/services/user.service.ts
features/product/services/product.service.ts

Avoid placing all services in a single folder
Keeps services closely aligned with features

c) Core Services for Application-Wide Logic

core/services/auth.service.ts
core/services/logger.service.ts
core/services/http-interceptor.service.ts

Core services are imported only once in AppModule
Provides singleton pattern for app-wide services

5. Structuring Components for Maintainability

a) Component Folder Structure

Organize components inside each feature module:

features/user/
 ├─ components/
 │   ├─ user-list/
 │   │   ├─ user-list.component.ts
 │   │   ├─ user-list.component.html
 │   │   └─ user-list.component.css
 │   └─ user-detail/
 │       ├─ user-detail.component.ts
 │       └─ user-detail.component.html

Each component has its own folder
Contains TypeScript, template, and styles

b) Use Smart vs Presentational Components

Smart components: Handle data fetching and state management
Presentational components: Display data and raise events

Example:

// Smart component
export class UserContainerComponent {
  users$ = this.userService.getUsers();
}

// Presentational component
export class UserListComponent {
  @Input() users: any[];
  @Output() select = new EventEmitter<number>();
}

Separates concerns and improves testability

6. Structuring Modules for Scalability

a) Feature Module Example

@NgModule({
  declarations: [
UserListComponent,
UserDetailComponent,
UserContainerComponent  ],
  imports: [
CommonModule,
SharedModule,
UserRoutingModule  ]
})
export class UserModule {}

Imports SharedModule for reusable components
Contains its own routing module

b) Root Module Example

@NgModule({
  declarations: [AppComponent],
  imports: [
BrowserModule,
AppRoutingModule,
CoreModule,
SharedModule  ],
  bootstrap: [AppComponent]
})
export class AppModule {}

Minimal components
Imports core, shared, and feature modules as needed

7. Routing Best Practices

Use feature-specific routing modules with RouterModule.forChild()
Keep root routing minimal
Lazy load feature modules wherever possible

const routes: Routes = [
  { path: 'users', loadChildren: () => import('./features/user/user.module').then(m => m.UserModule) },
  { path: 'products', loadChildren: () => import('./features/product/product.module').then(m => m.ProductModule) }
];

8. Testing and Maintainability

Write unit tests for services and components
Feature modules make it easier to test modules independently
Shared modules can be tested for reusable components