Interview Preparation With Bipin — Let’s Crack the Interviews!

## 🚨 1. Performance Issues * Your API response time suddenly increased from 200ms to 3 seconds. How will you debug it? * One microservice is slow, but others are fine. How do you isolate the issue? * Database CPU is 100%. What steps will you take? * Application memory usage keeps increasing over time—how will you find root cause? * High GC (Garbage Collection) in .NET app—how do you handle it? --- ## 🔥 2. Production Failures / Downtime * A critical microservice is down in production. What will you do? * How do you design system to handle partial failures? * What happens if Kafka goes down in production? * One dependency service is slow/unavailable—how do you protect your system? * How do you ensure zero-downtime deployment? --- ## 🧠 3. Microservices & Communication Issues * One service is calling another service and causing cascading failure—how will you fix it? * How do you handle synchronous vs asynchronous communication in production? * How do you prevent tight coupling betwe...

                                               SECTION 1: C# FUNDAMENTALS Q1. What is the difference between Abstract class vs Interface? Abstract Class: can have implementation (concrete methods), fields, constructors, access modifiers. Supports single inheritance only. Used for IS-A relationships among related classes.  Interface : pure contract — method signatures (before C# 8), no fields, no constructors, all public by default. Multiple interfaces allowed. Used for IS-WHAT (capability) relationships. Code: // Abstract class public abstract class Shape {     public string Color = "Red"; // field allowed     public abstract double Area(); // must override     public virtual void Print() => // can override         Console.WriteLine($"Color: {Color}"); } // Interface public interface IDrawable { void Draw(); } ...