Coding Interview Resources

Three-Tier Architecture
__ _

Three-tier architecture is a software design pattern that separates an application into three layers: presentation, business logic, and data. This separation promotes scalability, maintainability, and flexibility.

1️⃣Presentation Layer (Client Tier)

   - Role: Manages the user interface.
   - Components: Web browsers, mobile apps.
   - Technologies: HTML, CSS, JavaScript.
  
2️⃣Business Logic Layer (Application Tier)

   - Role: Processes business logic and rules.
   - Components: Application servers.
   - Technologies: Java, .NET, Python.
  
3️⃣Data Layer (Data Tier)

   - Role: Manages data storage and retrieval.
   - Components: Database servers.
   - Technologies: SQL, NoSQL databases.

How to guess the solution for DSA problems?

Yes, it is possible.

You can predict the solution for a problem by analyzing the constraints.

Curious if you need a greedy approach or a backtracking solution? Trying to decide between an O(n^3) or an O(n log n) approach? Just scroll down the LeetCode question and look at the constraints of the main element.

Wondering if you should use dynamic programming or plain recursion? Should your solution be O(n^2) or O(n)? Simply examine the constraints of the main variable.

Here's a quick guide based on the value of (n):

- If n <= 12 Time complexity can be O(n!).
- If n <= 25 Time complexity can be O(2^n).
- If n <= 100 Time complexity can be O(n^4).
- If n <= 500 Time complexity can be O(n^3).
- If n <= 10 ^ 4 Time complexity can be O(n^2).
- If n <= 10 ^ 6 Time complexity can be O(n log n).
- If n <= 10 ^ 8 Time complexity can be O(n).
- If n > 10 ^ 8 Time complexity can be O(log n) or 0(1).
- If n <= 10 ^ 9 Time complexity can be O(sqrt{n}).
- If n > 10 ^ 9 Time complexity can be O(log n) or 0(1).

Understanding these constraints can help you choose the right algorithm and improve your problem-solving efficiency.

Best DSA RESOURCES: https://topmate.io/coding/886874

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25+ essential tools specifically for tech and developer students 🔖
https://t.me/AI_Best_Tools/301

Beginner’s Roadmap to Learn Data Structures & Algorithms

1. Foundations: Start with the basics of programming and mathematical concepts to build a strong foundation.

2. Data Structure: Dive into essential data structures like arrays, linked lists, stacks, and queues to organise and store data efficiently.

3. Searching & Sorting: Learn various search and sort techniques to optimise data retrieval and organisation.

4. Trees & Graphs: Understand the concepts of binary trees and graph representation to tackle complex hierarchical data.

5. Recursion: Grasp the principles of recursion and how to implement recursive algorithms for problem-solving.

6. Advanced Data Structures: Explore advanced structures like hashing, heaps, and hash maps to enhance data manipulation.

7. Algorithms: Master algorithms such as greedy, divide and conquer, and dynamic programming to solve intricate problems.

8. Advanced Topics: Delve into backtracking, string algorithms, and bit manipulation for a deeper understanding.

9. Problem Solving: Practice on coding platforms like LeetCode to sharpen your skills and solve real-world algorithmic challenges.

10. Projects & Portfolio: Build real-world projects and showcase your skills on GitHub to create an impressive portfolio.

Best DSA RESOURCES: https://topmate.io/coding/886874

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Here are the top 16 OOP interview questions👇

1. What is the difference between a class and an object?
2. What is the difference between a static and non-static method?
3. What is the purpose of an interface in OOP?
4. Explain the 4 pillars of OOP.
5. What is the difference between a public and private constructor?
6. What is the difference between an abstract class and an interface?
7. What is the difference between a shallow copy and a deep copy?
8. What is the role of the "this" keyword in OOP?
9. What is a virtual function, and how is it implemented in OOP?
10. What is the difference between overloading and overriding a method? 11. What is an Abstract class?
12. Explain different types of constructors.
13. What is Coupling in OOP and why is it helpful?
14. What is a destructor in OOP?
15. What is a static keyword in cpp?
16. What is the difference between encapsulation and data abstraction?

Best DSA RESOURCES: https://topmate.io/coding/886874

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Stop blaming others when you find a bug.

Instead, focus on fixing it.

If someone introduces a bug, it is not their fault.

It is OUR fault. We made the mistake as a team. We own the code together.

The most important is to fix the problem and learn from it.

Remember that you're all in the same boat. If the boat has a hole in it, don't waste time blaming each other.

Instead, work together to fix the hole before everyone sinks.

𝐄𝐯𝐞𝐫𝐲 𝐄𝐧𝐠𝐢𝐧𝐞𝐞𝐫 𝐌𝐮𝐬𝐭 𝐊𝐧𝐨𝐰 𝐭𝐡𝐞 𝐓𝐨𝐩 𝟕 𝐀𝐫𝐜𝐡𝐢𝐭𝐞𝐜𝐭𝐮𝐫𝐚𝐥 𝐏𝐚𝐭𝐭𝐞𝐫𝐧𝐬

An architectural pattern is a general, reusable solution to common problems in software design. It structures and organises software systems to address specific concerns like scalability, maintainability, flexibility, and efficiency.

1. Microservices Architecture:
Divides an app into small, independent services with APIs.
Example: Netflix - separate services for user management, content streaming, and recommendations.

2. Layered Architecture:
Divides an app into layers (presentation, logic, data) for specific functions.
Example: JavaEE apps - distinct layers for UI, business logic, and data access.

3. Event-Driven Architecture:
Components communicate through events for loose coupling.
Example: Airbnb uses Apache Kafka for real-time event processing like booking requests.

4. Model-View-Controller (MVC) Architecture:
Splits an app into Model (data), View (UI), and Controller (logic).
Example: Ruby on Rails apps - separation of data, interface, and user input handling.

5. Master-Slave Architecture:
One master coordinates multiple slaves' tasks.
Example: Database replication - master for writes, slaves for reads, as seen in many systems.

6. Monolithic Architecture:
Entire app bundled together as a single unit.
Example: Traditional enterprise software - all features in a single executable.

7. Service-Oriented Architecture (SOA):
App composed of reusable, loosely coupled services.
Example: Salesforce - integrated or standalone sales, support, and marketing services.

Each pattern offers unique advantages and trade-offs, depending on the project's requirements and complexities.

Best DSA RESOURCES: https://topmate.io/coding/886874

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Java Developer Interview ❤
It'll gonna be super helpful for YOU

𝗧𝗼𝗽𝗶𝗰 𝟭: 𝗣𝗿𝗼𝗷𝗲𝗰𝘁 𝗳𝗹𝗼𝘄 𝗮𝗻𝗱 𝗮𝗿𝗰𝗵𝗶𝘁𝗲𝗰𝘁𝘂𝗿𝗲
- Please tell me about your project and its architecture, Challenges faced?
- What was your role in the project? Tech Stack of project? why this stack?
- Problem you solved during the project? How collaboration within the team?
- What lessons did you learn from working on this project?
- If you could go back, what would you do differently in this project?

𝗧𝗼𝗽𝗶𝗰 𝟮: 𝗖𝗼𝗿𝗲 𝗝𝗮𝘃𝗮
- String Concepts/Hashcode- Equal Methods
- Immutability
- OOPS concepts
- Serialization
- Collection Framework
- Exception Handling
- Multithreading
- Java Memory Model
- Garbage collection

Tech Community
👉 t.me/Java_Programming_Notes

𝗧𝗼𝗽𝗶𝗰 𝟯: 𝗝𝗮𝘃𝗮-𝟴/𝗝𝗮𝘃𝗮-𝟭𝟭/𝗝𝗮𝘃𝗮𝟭𝟳
- Java 8 features
- Default/Static methods
- Lambda expression
- Functional interfaces
- Optional API
- Stream API
- Pattern matching
- Text block
- Modules

𝗧𝗼𝗽𝗶𝗰 𝟰: 𝗦𝗽𝗿𝗶𝗻𝗴 𝗙𝗿𝗮𝗺𝗲𝘄𝗼𝗿𝗸, 𝗦𝗽𝗿𝗶𝗻𝗴-𝗕𝗼𝗼𝘁, 𝗠𝗶𝗰𝗿𝗼𝘀𝗲𝗿𝘃𝗶𝗰𝗲, 𝗮𝗻𝗱 𝗥𝗲𝘀𝘁 𝗔𝗣𝗜
- Dependency Injection/IOC, Spring MVC
- Configuration, Annotations, CRUD
- Bean, Scopes, Profiles, Bean lifecycle
- App context/Bean context
- AOP, Exception Handler, Control Advice
- Security (JWT, Oauth)
- Actuators
- WebFlux and Mono Framework
- HTTP methods
- JPA
- Microservice concepts
- Spring Cloud

𝗧𝗼𝗽𝗶𝗰 𝟱: 𝗛𝗶𝗯𝗲𝗿𝗻𝗮𝘁𝗲/𝗦𝗽𝗿𝗶𝗻𝗴-𝗱𝗮𝘁𝗮 𝗝𝗽𝗮/𝗗𝗮𝘁𝗮𝗯𝗮𝘀𝗲 (𝗦𝗤𝗟 𝗼𝗿 𝗡𝗼𝗦𝗤𝗟)
- JPA Repositories
- Relationship with Entities
- SQL queries on Employee department
- Queries, Highest Nth salary queries
- Relational and No-Relational DB concepts
- CRUD operations in DB
- Joins, indexing, procs, function

𝗧𝗼𝗽𝗶𝗰 𝟲: 𝗖𝗼𝗱𝗶𝗻𝗴
- DSA Related Questions
- Sorting and searching using Java API.
- Stream API coding Questions

Tech Jobs and Internships
t.me/getjobss

𝗧𝗼𝗽𝗶𝗰 𝟳: 𝗗𝗲𝘃𝗼𝗽𝘀 𝗾𝘂𝗲𝘀𝘁𝗶𝗼𝗻𝘀 𝗼𝗻 𝗱𝗲𝗽𝗹𝗼𝘆𝗺𝗲𝗻𝘁 𝗧𝗼𝗼𝗹𝘀
- These types of topics are mostly asked by managers or leads who are heavily working on it, That's why they may grill you on DevOps/deployment-related tools, You should have an understanding of common tools like Jenkins, Kubernetes, Kafka, Cloud, and all.

𝗧𝗼𝗽𝗶𝗰𝘀 𝟴: 𝗕𝗲𝘀𝘁 𝗽𝗿𝗮𝗰𝘁𝗶𝗰𝗲
- The interviewer always wanted to ask about some design patterns, it may be Normal design patterns like singleton, factory, or observer patterns to know that you can use these in coding.

PDFs and Notes 📝
t.me/Java_Programming_Notes

Best Programming Resources: https://topmate.io/coding/886839

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DSA + DEVELOPMENT (Daily Schedule) 👨🏻‍💻

Morning:
- 9:00 AM - 10:30 AM: DSA Practice
- 10:30 AM - 11:00 AM: Break
- 11:00 AM - 12:30 PM: DSA Study/Review

Lunch:
- 12:30 PM - 1:30 PM: Lunch and Rest

Afternoon:
- 1:30 PM - 3:00 PM: MERN Development
- 3:00 PM - 3:30 PM: Break
- 3:30 PM - 5:00 PM: MERN Development

Evening:
- 5:00 PM - 6:00 PM: Review and Debug
- 6:00 PM - 7:00 PM: Dinner and Rest

Late Evening:
- 7:00 PM - 8:00 PM: Personal Development
- 8:00 PM - 9:00 PM: Reflect and Plan

Best DSA RESOURCES: https://topmate.io/coding/886874

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Important Topics for DSA

1. Week 1: Foundation
- Arrays & Linked Lists: Understand how to store and manage a list of elements.
- Stacks & Queues: Learn the Last-In-First-Out (LIFO) and First-In-First-Out (FIFO) principles.
- Searching & Sorting Techniques: Master basic algorithms for finding and organizing data.

2. Week 2: Intermediate
- Trees & Graphs: Study hierarchical and network data structures.
- Hashing & Hash Tables: Learn efficient methods for data retrieval.
- Dynamic Programming: Break problems into simpler sub-problems and solve them.

3. Week 3: Advanced
- Advanced Tree & Graph Algorithms: Delve deeper into complex traversal techniques.
- Heaps & Priority Queues: Understand specialized data structures for efficient prioritization.
- Backtracking & Recursion: Tackle problems with recursive solutions.

4. Week 4: DSA Hackathon
- Participate in coding challenges to solidify your learning and apply your skills.

Few Tips for Mastering DSA

1. Start Simple: Begin with easy problems and gradually move to more complex ones.
2. Practice Regularly: Consistency is key. Solve problems daily to improve your skills.
3. Understand Concepts: Don’t just memorize algorithms. Understand how and why they work.
4. Use Resources: Take advantage of online tutorials, courses, and coding platforms.
5. Join Communities: Engage with coding communities for support, motivation, and knowledge sharing.
6. Participate in Challenges: Join hackathons and coding contests to test your skills in real scenarios.

Best DSA RESOURCES: https://topmate.io/coding/886874

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𝗰𝗵𝗲𝗮𝘁𝘀𝗵𝗲𝗲𝘁 𝗳𝗼𝗿 𝗔𝗟𝗟 𝗲𝘀𝘀𝗲𝗻𝘁𝗶𝗮𝗹 𝗴𝗶𝘁 𝗰𝗼𝗺𝗺𝗮𝗻𝗱𝘀:

0. 𝗴𝗶𝘁 𝗶𝗻𝗶𝘁: Initializes a new Git repository.
1. 𝗴𝗶𝘁 𝗰𝗹𝗼𝗻𝗲 [𝘂𝗿𝗹]: Creates a local copy of a remote repository.
2. 𝗴𝗶𝘁 𝘀𝘁𝗮𝘁𝘂𝘀: Displays the state of the working directory and staging area.
3. 𝗴𝗶𝘁 𝗮𝗱𝗱 [𝗳𝗶𝗹𝗲]: Adds a file to the staging area.
4. 𝗴𝗶𝘁 𝗿𝗲𝘀𝗲𝘁 [𝗳𝗶𝗹𝗲]: Unstages a file while retaining the changes.
5. 𝗴𝗶𝘁 𝗱𝗶𝗳𝗳 --𝘀𝘁𝗮𝗴𝗲𝗱: Shows differences between the staging area and the last commit.
6. 𝗴𝗶𝘁 𝗰𝗼𝗺𝗺𝗶𝘁 -𝗺 "[𝗺𝗲𝘀𝘀𝗮𝗴𝗲]": Records staged changes with a descriptive message.
7. 𝗴𝗶𝘁 𝗯𝗿𝗮𝗻𝗰𝗵: Lists all local branches.
8. 𝗴𝗶𝘁 𝗰𝗵𝗲𝗰𝗸𝗼𝘂𝘁 -𝗯 [𝗻𝗮𝗺𝗲]: Creates and switches to a new branch.
9. 𝗴𝗶𝘁 𝗹𝗼𝗴: Displays commit history.
10. 𝗴𝗶𝘁 𝗿𝗲𝗺𝗼𝘁𝗲 𝗮𝗱𝗱 [𝗿𝗲𝗳] [𝘂𝗿𝗹]: Adds a new remote repository.
11. 𝗴𝗶𝘁 𝗽𝘂𝘀𝗵 [𝗮𝗹𝗶𝗮𝘀] [𝗯𝗿𝗮𝗻𝗰𝗵]: Uploads local branch commits to a remote repository.
12. 𝗴𝗶𝘁 𝗽𝘂𝗹𝗹: Fetches and merges changes from the remote to the local repository.
13. 𝗴𝗶𝘁 𝘀𝘁𝗮𝘀𝗵: Temporarily stores modified tracked files.
14. 𝗴𝗶𝘁 𝘀𝘁𝗮𝘀𝗵 𝗽𝗼𝗽: Restores the most recently stashed files.
15. 𝗴𝗶𝘁 𝘀𝘁𝗮𝘀𝗵 𝗱𝗿𝗼𝗽: Discards the most recently stashed changeset.
16. 𝗴𝗶𝘁 𝗿𝗲𝗯𝗮𝘀𝗲 [𝗯𝗿𝗮𝗻𝗰𝗵]: Reapplies commits on top of another base tip.
17. 𝗴𝗶𝘁 𝗿𝗲𝗯𝗮𝘀𝗲 -𝗶 𝗛𝗘𝗔𝗗~<𝗻>: Starts an interactive rebase for the last n commits.
18. 𝗴𝗶𝘁 𝗿𝗲𝘀𝗲𝘁 --𝗵𝗮𝗿𝗱 [𝗰𝗼𝗺𝗺𝗶𝘁]: Resets the working directory to a specified commit.
19. 𝗴𝗶𝘁 𝗹𝗼𝗴 𝗯𝗿𝗮𝗻𝗰𝗵𝗕..𝗯𝗿𝗮𝗻𝗰𝗵𝗔: Shows commits on branchA that are not on branchB.
20. 𝗴𝗶𝘁 𝗱𝗶𝗳𝗳 𝗯𝗿𝗮𝗻𝗰𝗵𝗕...𝗯𝗿𝗮𝗻𝗰𝗵𝗔: Displays differences between two branches.
21. 𝗴𝗶𝘁 𝘀𝗵𝗼𝘄 [𝗦𝗛𝗔]: Shows the changes in a specific commit.
22. 𝗴𝗶𝘁 𝗰𝗼𝗻𝗳𝗶𝗴 --𝗴𝗹𝗼𝗯𝗮𝗹 𝗰𝗼𝗿𝗲.𝗲𝘅𝗰𝗹𝘂𝗱𝗲𝘀𝗳𝗶𝗹𝗲 [𝗳𝗶𝗹𝗲]: Sets up a global file for ignoring files.

Best DSA RESOURCES: https://topmate.io/coding/886874

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Is DSA important for interviews?

Yes, DSA (Data Structures and Algorithms) is very important for interviews, especially for software engineering roles.

I often get asked, What do I need to start learning DSA?

Here's the roadmap for getting started with Data Structures and Algorithms (DSA):

𝗣𝗵𝗮𝘀𝗲 𝟭: 𝗙𝘂𝗻𝗱𝗮𝗺𝗲𝗻𝘁𝗮𝗹𝘀
1. Introduction to DSA
- Understand what DSA is and why it's important.
- Overview of complexity analysis (Big O notation).

2. Complexity Analysis
- Time Complexity
- Space Complexity

3. Basic Data Structures
- Arrays
- Linked Lists
- Stacks
- Queues

4. Basic Algorithms
- Sorting (Bubble Sort, Selection Sort, Insertion Sort)
- Searching (Linear Search, Binary Search)

5. OOP (Object-Oriented Programming)

𝗣𝗵𝗮𝘀𝗲 𝟮: 𝗜𝗻𝘁𝗲𝗿𝗺𝗲𝗱𝗶𝗮𝘁𝗲 𝗖𝗼𝗻𝗰𝗲𝗽𝘁𝘀
1. Two Pointers Technique
- Introduction and basic usage
- Problems: Pair Sum, Triplets, Sorted Array Intersection etc..

2. Sliding Window Technique
- Introduction and basic usage
- Problems: Maximum Sum Subarray, Longest Substring with K Distinct Characters, Minimum Window Substring etc..

3. Line Sweep Algorithms
- Introduction and basic usage
- Problems: Meeting Rooms II, Skyline Problem

4. Recursion

5. Backtracking

6. Sorting Algorithms
- Merge Sort
- Quick Sort

7. Data Structures
- Hash Tables
- Trees (Binary Trees, Binary Search Trees)
- Heaps

𝗣𝗵𝗮𝘀𝗲 𝟯: 𝗔𝗱𝘃𝗮𝗻𝗰𝗲𝗱 𝗖𝗼𝗻𝗰𝗲𝗽𝘁𝘀
1. Graph Algorithms
- Graph Representation (Adjacency List, Adjacency Matrix)
- BFS (Breadth-First Search)
- DFS (Depth-First Search)
- Shortest Path Algorithms (Dijkstra's, Bellman-Ford)
- Minimum Spanning Tree (Kruskal's, Prim's)

2. Dynamic Programming
- Basic Problems (Fibonacci, Knapsack etc..)
- Advanced Problems (Longest Increasing Subsea mice, Matrix Chain Subsequence, Multiplication etc..)

3. Advanced Trees
- AVL Trees
- Red-Black Trees
- Segment Trees
- Trie

𝗣𝗵𝗮𝘀𝗲 𝟰: 𝗣𝗿𝗮𝗰𝘁𝗶𝗰𝗲 𝗮𝗻𝗱 𝗔𝗽𝗽𝗹𝗶𝗰𝗮𝘁𝗶𝗼𝗻
1. Competitive Programming Platforms: LeetCode, Codeforces, HackerRank, CodeChef Solve problems daily

2. Mock Interviews
- Participate in mock interviews to simulate real interview scenarios.
- DSA interviews assess your ability to break down complex problems into smaller steps.

Best DSA RESOURCES: https://topmate.io/coding/886874

All the best 👍👍

𝗚𝗶𝘁 𝗘𝘀𝘀𝗲𝗻𝘁𝗶𝗮𝗹𝘀: 𝗬𝗼𝘂𝗿 𝗰𝗵𝗲𝗮𝘁 𝘀𝗵𝗲𝗲𝘁 𝗳𝗼𝗿 𝗺𝗮𝘀𝘁𝗲𝗿𝗶𝗻𝗴 𝘃𝗲𝗿𝘀𝗶𝗼𝗻 𝗰𝗼𝗻𝘁𝗿𝗼𝗹 👨💻


Whether you're a seasoned developer or just starting out, Git is an essential tool for seamless collaboration and efficient workflows. Here's a quick recap of the most common Git commands to keep you on track:

✨𝗚𝗲𝘁𝘁𝗶𝗻𝗴 𝗦𝘁𝗮𝗿𝘁𝗲𝗱:
git init: Initializes a new Git repository.
git clone <repo_url>: Clones an existing repository to your local machine.

📄𝗧𝗿𝗮𝗰𝗸𝗶𝗻𝗴 𝗖𝗵𝗮𝗻𝗴𝗲𝘀:
git status: Checks the status of files in your working directory.
git add <file> or git add .: Stages files for commit.

✅𝗖𝗼𝗺𝗺𝗶𝘁𝘁𝗶𝗻𝗴 𝗪𝗼𝗿𝗸:
git commit -m "message": Commits staged changes with a descriptive message.

🔀𝗕𝗿𝗮𝗻𝗰𝗵𝗶𝗻𝗴 𝗮𝗻𝗱 𝗠𝗲𝗿𝗴𝗶𝗻𝗴:
git branch: Lists existing branches.
git branch <new_branch>: Creates a new branch.
git checkout <branch>: Switches to a different branch.
git merge <branch>: Merges changes from one branch into another.
git checkout -b <new_branch>: Creates and switches to a new branch.

👨💻𝗥𝗲𝗺𝗼𝘁𝗲 𝗖𝗼𝗹𝗹𝗮𝗯𝗼𝗿𝗮𝘁𝗶𝗼𝗻:
git remote -v: Lists remote repositories.
git fetch origin <branch>: Fetches changes from a remote branch.
git merge origin/<branch>: Merges fetched changes into the current branch.
git push origin <branch>: Pushes local changes to a remote branch.

🔎𝗧𝗿𝗮𝗰𝗸𝗶𝗻𝗴 𝗛𝗶𝘀𝘁𝗼𝗿𝘆:
git log: Shows a list of commits.
git log --oneline: Displays a condensed commit history.

⏪𝗨𝗻𝗱𝗼𝗶𝗻𝗴 𝗠𝗶𝘀𝘁𝗮𝗸𝗲𝘀:
git revert <commit>: Reverses a specific commit.
git reset --hard HEAD: Resets the working directory to the last commit (use with caution!).

𝗧𝗮𝗴𝗴𝗶𝗻𝗴 𝗠𝗶𝗹𝗲𝘀𝘁𝗼𝗻𝗲𝘀:
git tag: Lists existing tags.
git tag -a v1.0 -m "tag": Creates a new tag for a specific commit.

⚙𝗖𝗼𝗻𝗳𝗶𝗴𝘂𝗿𝗮𝘁𝗶𝗼𝗻:
git config --global user. name "name": Sets your global Git username.
git config --global user. email "email": Sets your global Git email.

Commonly asked System Design CONCEPT BASED interview topics -

1. Horizontal vs Vertical Partitioning
2. Apache Kafka
3. Rate Limiter
4. JWT vs OAuth vs SAML
5. Single Sign-On (SSO)
6. Microservices vs Monolithic Architecture
7. Reverse Proxy vs Forward Proxy
8. CAP Theorem
9. Global Scale System Design
10. Efficient Caching Strategy

To learn these topics in detail go through the post:

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All the best 👍👍

Software Developers => Let's understand, 𝐑𝐚𝐛𝐛𝐢𝐭𝐌𝐐 (Give it a read 👇)

RabbitMQ =>born in 2007 => a joint venture between LShift and CohesiveFT, aimed to provide an open-source, reliable message broker implementing the AMQP standard.

RabbitMQ is written in Erlang.

It is -

◾ an open-source message broker software that implements the Advanced Message Queuing Protocol (AMQP).

** AMQP => a binary protocol, meaning it encodes data in a compact binary format for efficient transmission over networks.

◾ a robust intermediary between different applications or components of a system, facilitating the exchange of messages in a reliable and scalable manner.

◾ known for its fault tolerance, concurrency and distributed systems capabilities.

◾ operating primarily on a 𝐩𝐮𝐬𝐡-𝐛𝐚𝐬𝐞𝐝 𝐦𝐨𝐝𝐞𝐥 for message delivery

📌 𝐂𝐨𝐫𝐞 𝐂𝐨𝐦𝐩𝐨𝐧𝐞𝐧𝐭𝐬
[1.] Producer
◾ An application that creates and sends messages to RabbitMQ.

[2.] Consumer
An application that receives messages from RabbitMQ.

[3.] Queue
◾ A named buffer where messages are stored.

[4.] Exchange
◾ The component that receives messages from producers and routes them to the appropriate queues based on specific rules.
◾ The heart of an exchange is its routing algorithm, which determines how messages are directed to queues.

Main exchange types -
◾ Direct - Matches the routing key of the message exactly with the binding key of a queue.
◾ Fanout - Broadcasts the message to all queues bound to the exchange.
◾ Topic - Uses wildcards (* and #) to match routing keys to binding keys.

[5.] Binding
A link between a queue and an exchange, specifying the routing criteria for messages.

📌 𝐇𝐨𝐰 𝐈𝐭 𝐖𝐨𝐫𝐤𝐬 𝐈𝐧𝐭𝐞𝐫𝐧𝐚𝐥𝐥𝐲?
1. The producer connects to RabbitMQ and publishes a message to an exchange.
2. The message includes routing information (e.g. => a routing key).
3. The exchange receives the message and examines the routing key.
4. Based on its configuration and bindings, the exchange determines which queues should receive the message.
5. The message is delivered to the designated queues, where it waits to be consumed.
6. Consumers connect to RabbitMQ and subscribe to specific queues.
7. When a message becomes available in the queue, RabbitMQ delivers it to one of the subscribed consumers.
8. After a consumer processes a message, it sends an acknowledgment to RabbitMQ, confirming that the message was successfully received and processed.
9. If no acknowledgment is received within a specified time, RabbitMQ can redeliver the message to another consumer.

📌 𝐅𝐥𝐨𝐰 𝐂𝐨𝐧𝐭𝐫𝐨𝐥
1. RabbitMQ uses credit-based flow control to prevent consumers from being overwhelmed with messages.
2. Consumers request a certain number of messages (credit) from the broker, and the broker delivers messages up to that limit.
3. When the consumer acknowledges a message, it receives additional credit, allowing the broker to send more messages.

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All the best 👍👍

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