Subject Interface (INewsPublisher): ● This interface defines methods for subscribing, unsubscribing, and notifying observers. The subject manages a list of observers and notifies them when there is

Answer: n update. public interface INewsPublisher { void Subscribe(IObserver observer); void Unsubscribe(IObserver observer); void Notify(string news); }

What interviewers expect

• A clear definition tied to GoF Patterns in Gang of Four Patterns projects
• Trade-offs (performance, maintainability, security, cost)
• When you would and would not use it in production

Real-world example

In a production Gang of Four Patterns application, teams apply this when handling user-facing features or integration boundaries. For example, you might use it during a sprint where reliability and observability matter—logging metrics, validating edge cases, and documenting the decision in an ADR so future developers understand why the approach was chosen.

How to explain in the interview

1. Define the concept in one or two sentences.
2. Context — where it fits in Gang of Four Patterns architecture.
3. Example — a specific project, bug, or performance win.
4. Trade-off — what you gain vs what you sacrifice.

Tip: Practice aloud on Toolliyo mock interview or the Interview Q&A section before your real interview.