Guards control client navigation and user experience. The server must independently authorize every protected operation because client code can be bypassed.
Before you start
You should understand a component’s class, template and dependencies. Follow both the framework lifecycle and the ownership of each value or resource. Apply examples inside an Angular application; the surrounding application configuration and imports depend on the feature being demonstrated.
The practical goal is to reason through this situation: A guard redirects an unsigned-in visitor away from an account page. Read the walkthrough first, then try the interview exercise before opening its answer. The important part is explaining the decision and its consequences, rather than remembering a definition alone.
Step-by-step walkthrough
Step 1: Define navigation behavior
A guard can redirect an unsigned-in visitor before the protected page becomes active. This improves the client experience.
Step 2: Authorize the operation
Every protected API request must verify the authenticated user and their permission to access that resource.
Step 3: Test independent boundaries
Call the API directly without navigating through the guarded route. The server must still reject unauthorized access.
Worked scenario
A guard redirects an unsigned-in visitor away from an account page.
An admin page guard hides navigation from ordinary users, but its delete endpoint still receives direct HTTP calls. The endpoint checks identity and authorization before modifying data. Downloaded JavaScript and hidden buttons are not access controls; successful client navigation does not establish permission for a later server operation.
Common mistake
Hiding a route does not secure its API or downloaded JavaScript.
Verify the behavior
Test signed-out, ordinary and privileged users at both route and API boundaries, including access to another user’s resource.
Interview exercise
Secure an administrative mutation.
Answer and reasoning
Check identity and authorization at the server boundary, then use guards to provide understandable navigation behavior.
Continue learning
Compare the scenario with the Angular interview questions and test your understanding with the Angular MCQs. For terminology and implementation details, consult the reference material.