🔹 OOPS Beyond Theory

• Why OOPS changed software development
• Real-time problems solved using OOPS
• Encapsulation in Banking Applications
• Inheritance Problems & Tight Coupling
• Composition vs Inheritance (Real Project Scenarios)
• Polymorphism in Payment Gateway Systems
• Abstraction
• SOLID Principles Introduction

🔹 JVM Architecture Deep Dive

• How Java Code Executes Internally
• JVM Components Explained Visually
• Heap Memory vs Stack Memory
• Metaspace vs PermGen
• ClassLoader Internal Working
• Object Creation Flow Inside JVM
• Why StackOverflowError Happens
• Why OutOfMemoryError Happens
• Memory Leaks in Real Applications

🔹 Garbage Collector Internals

• Why Garbage Collection Needed
• How Objects Become Eligible for GC
• Minor GC vs Major GC
• Stop The World Event
• Serial GC vs Parallel GC vs G1 GC
• How Modern JVM Optimizes Memory
• GC Tuning Basics

🔥 Multithreading Deep Dive

🔹 Why Multithreading?

• Why Single Thread Becomes Slow
• Real-Time Backend Processing Examples
• How Applications Handle Millions of Requests

🔹 Synchronization Deep Dive

• Race Conditions Explained
• Critical Section Problem
• synchronized Keyword Internals
• Object Lock vs Class Lock
• Deadlock Detection & Prevention
• volatile Keyword
• Atomic Classes

🔹 Why Executor Framework Came?

• Problems with Manual Thread Creation
• Thread Pool Internal Working
• FixedThreadPool vs CachedThreadPool
• Future & Callable
• Real-Time Async Processing

🔹 CompletableFuture Deep Dive

• Why Future Was Not Enough
• Async Programming in Modern Java
• Parallel API Calls
• Non-Blocking Backend Processing
• Chaining Async Operations
• Exception Handling in Async Flow
• Real Project Use Cases

🔹 Why Collections Framework?

• Problems with Arrays
• Dynamic Data Handling

🔹 HashMap Internal Working

• Bucket Structure Explained
• Hashing Algorithm
• Collision Handling
• equals() vs hashCode()
• LinkedList to Tree Conversion

🔹 ConcurrentHashMap

• Why HashMap Fails in Multithreading
• Segment Locking
• Thread-Safe Collections
• Internal Concurrency Optimization

🔹 Immutable Objects

• Why Immutable Objects Are Powerful
• String Immutability Internals
• Creating Custom Immutable Classes
• Immutable Collections
• Real Benefits in Multithreading

🔹 Why Java 8 Changed Java Industry

• Functional Programming Introduction
• Lambda Expressions
• Functional Interfaces
• Stream API Internal Working
• Parallel Streams
• Method References
• Optional Class
• Date & Time API

🔹 Stream API Deep Dive

• map vs flatMap
• filter vs reduce
• Grouping & Partitioning
• Stream Pipeline Internals
• Real-Time Data Processing
• Most Important Interview Related Questions Discussion

🔹 Singleton Pattern

• Why Singleton Needed
• Thread-Safe Singleton
• Singleton Problems

🔹 Factory Pattern

• Object Creation Problem
• Loose Coupling
• Factory Pattern in Spring Framework

🔹 Strategy Pattern

• How we design our classes
• Dynamic Runtime Behavior Change
• Payment System Real Example

🔹 Builder Pattern

• Constructor Problems
• Immutable Object Creation
• Builder Pattern in Enterprise Applications

🔹 Why Spring Framework?

• Tight Coupling Issues
• Enterprise Application Challenges

🔹 Spring Architecture Internals

• IOC Container Internal Working
• Dependency Injection Explained Internally
• BeanFactory vs ApplicationContext
• How Spring Creates Objects

🔹 Bean Lifecycle Deep Dive

• Bean Creation Flow
• Bean Initialization
• @PostConstruct & @PreDestroy
• Bean Scopes
• Singleton Bean Internals

🔹 @Configuration vs @Component

• Why Both Exist
• Proxy Object Creation
• Internal Difference
• Real Interview Questions

🔹 Spring Boot Internals

• Why Spring Boot Became Popular
• Auto Configuration Internals
• Starter Dependencies
• Embedded Tomcat Working
• Application Startup Flow

🔹 @SpringBootApplication Breakdown

• @Configuration
• @EnableAutoConfiguration
• @ComponentScan
• Internal Flow Explained

🔹 Why Security Needed?

• Authentication vs Authorization
• Session vs Token-Based Authentication

🔹 JWT Authentication Deep Dive

• Why JWT Came
• Stateless Authentication
• JWT Structure
• Access Token vs Refresh Token
• JWT Filter Internal Flow
• Spring Security Filter Chain
• Role-Based Authorization
• Secure REST APIs

🔹 Monolith vs Microservices

• Real Industry Comparison
• Scaling Problems in Monolith
• Independent Deployment
• Fault Tolurance

🔹 Microservices Design Principles

• Single Responsibility
• Database Per Service
• Loose Coupling
• High Cohesion
• Event-Driven Architecture

🔹 RestTemplate vs WebClient

• Why RestTemplate Became Limited
• Blocking vs Non-Blocking Calls
• Reactive Programming Basics
• WebClient Internal Working
• Async Service Communication
• Real Performance Comparison

🔹 Eureka Server

• Why Service Discovery Needed
• Dynamic Service Registration
• Load Balancing Basics

🔹 API Gateway

• Why API Gateway Came
• Centralized Routing
• Authentication Handling
• Request Filtering

🔹 Spring Cloud Gateway

• Dynamic Routing
• Gateway Filters
• Rate Limiting

🔹 Circuit Breaker (Resilience4j)

• Why Distributed Systems Fail
• Circuit Breaker States
• Fallback Mechanism

🔹 Retry Mechanism

• Temporary Failure Handling
• Retry Strategies
• Retry with Backoff

🔹 Timeout Handling

• Why Timeout Matters
• Preventing Resource Exhaustion
• API Failure Management

• Why APIs Need Protection
• Preventing API Abuse
• Gateway-Level Rate Limiting

🔹 Why Distributed Transactions Fail

• Problems with Traditional Transactions
• Eventual Consistency

🔹 Choreography-Based Saga

• Event-Driven Communication
• Kafka-Based Workflow
• Decentralized Transactions

🔹 Orchestration-Based Saga

• Centralized Transaction Coordinator
• Workflow Management
• Compensation Transactions

🔹 Kafka Fundamentals & Theory

• What is a Messaging System? (Point-to-Point vs. Pub/Sub)
• Why Kafka? What problems does it solve?
• Kafka Architecture Overview
• McDonald's Analogy for Clusters, Brokers, and Zookeeper

🔹 Core Kafka Concepts Demystified

• Events, Event Keys, Event Values, and Timestamps
• Kafka Topics and Partitions explained
• How Offsets work
• Leader and Follower roles for high availability
• How to guarantee processing order using Event Keys

🔹 Hands-On Coding with Spring Boot

• How to install and run Kafka locally (Mac/Linux)
• Creating Kafka Topics
• Building a Kafka Producer in Spring Boot using KafkaTemplate
• Sending JSON messages with serialization
• Building a Kafka Consumer in Spring Boot
• Real-time data flow from end-to-end

• Why Centralized Configuration Needed
• Dynamic Configuration Management
• Environment-Based Configurations

🔹 Docker Containerization

• Why Docker Changed Deployment
• VM vs Container
• Docker Image vs Container
• Dockerfile Deep Dive
• Multi-Stage Builds

🔹 CI/CD Pipeline

• Why Automation Needed
• GitHub Actions Workflow
• Automated Build & Deployment
• Testing Pipeline
• Production Deployment Flow

🔹 EC2 Deployment

• Hosting Spring Boot Applications
• Linux Server Basics

🔹 S3 Storage

• File Upload Systems
• Static Resource Hosting
• Secure File Access

🔹 AWS RDS Database

• API Testing using Postman
• Exception Handling Best Practices
• Clean Code Practices
• Real-Time Project Architecture
• Interview Preparation Sessions
• Resume Building Guidance
• Mock Interviews
• Real Enterprise Project Development