Angular's component lifecycle is a fundamental concept that every developer must understand to build efficient applications. From the moment a component is created until it is destroyed, Angular provides a series of lifecycle hooks that allow you to tap into key events during this process. These hooks, including ngOnInit, ngOnChanges, and ngOnDestroy, give you control over initialization, change detection, and cleanup. By mastering these hooks, you'll be able to optimize your components, manage resources better, and enhance your application's overall performance.

During the ngOnInit phase, components can retrieve data from services or perform initialization tasks. Similarly, with the ngOnChanges hook, developers can respond to input property changes, ensuring that the UI stays in sync with the underlying data model. Finally, the ngOnDestroy hook is crucial for cleaning up resources, such as unsubscribing from observables or detaching event listeners, thus preventing memory leaks. Understanding and leveraging these lifecycle hooks is essential for creating scalable, maintainable Angular applications.

When developing an Angular application, it's crucial to prioritize performance to enhance user experience. One of the top practices is to implement lazy loading. This technique allows you to load modules only when they are needed, significantly reducing the initial load time. Additionally, utilizing the Angular CLI can streamline your builds and ensure that unnecessary code is not included in production builds.

Another important practice is to minimize the use of change detection. By using the OnPush strategy, you can reduce the number of checks Angular performs, which can greatly improve performance. Furthermore, leveraging the trackBy function in your *ngFor loops helps in reducing DOM manipulations by only re-rendering changed items. Implementing these practices will significantly contribute to the overall performance of your Angular app.

Mastering Dependency Injection in Angular can significantly enhance your application's scalability and maintainability. By utilizing Angular's built-in dependency injection framework, you can efficiently manage the dependencies of your services, components, and other entities. One essential tip is to leverage the @Injectable decorator in your service classes. This allows Angular to understand how to instantiate your services and manage their lifecycle. To further master this concept, implement hierarchical injectors to create specialized services at different levels of your application, ensuring that your components receive only what they need, thereby adhering to the Single Responsibility Principle.

Additionally, consider using multi providers to inject multiple instances of a service where necessary. This approach can be particularly useful when you have different configurations of a service needed by various components. Here are a few tips to streamline your dependency injection:

1. Understand the injector hierarchy: Grasp how Angular creates and resolves dependencies based on their level in the component tree.
2. Use providedIn: Utilize the `providedIn` property of the @Injectable decorator to define how and where the services should be available in your application.
3. Keep it clean: Avoid circular dependencies by being mindful of how your services reference each other.