Backend:
1. What is API
2. REST API architecture
3. What is client-server architecture? What is HTTP? HTTP vs HTTPS
4. Query Params, Pagination, Sorting, Limit, Offset
5. What are tokens? What are API keys?
6. Environment Variables
7. What is JSON? What are JSON alternatives?
8. What are middlewares?
9. What are controllers?
10. What is OAuth?
11. What is CORS?
12. What is MVC pattern?
13. What is axios?
14. What is JWT
15. Authentication vs Authorization
16. Blocking IO vs Non-blocking IO
17. NodeJS architecture
18. Status codes
19. package.json vs package-lock.json
20. Why Express?
21. HTTP methods
22. PUT vs PATCH
23. SQL vs NoSQL

MongoDB and Mongoose:
1. NoSQL Basics (BASE)
2. Basic MongoDB CRUD operations
3. How to set up MongoDB, various ways
4. Need for Mongoose
5. MongoDB architecture: documents, collections
6. Cap Theorem

Git and GitHub:
1. Why Git is needed
2. Ways to set up Git
3. Git vs GitHub
4. GitHub commands
5. Clone, fork, merge, contribute

React:
1. React: why, what, advantages, disadvantages
2. SPA
3. React vs Angular
4. React Virtual DOM and Fiber, reconciliation
5. React lifecycle with functional components
6. All 7 fundamental hooks
7. CSR, SSG, SSR, ISG
8. Prop Drilling Issue
9. React Router, Redux, and other libraries used
10. useMemo vs useCallback
11. React Memo
12. Bundlers, JSX, Vite, Babel idea
13. Context API
14. How to improve speed in React
15. Lazy Loading (Suspense + Error Boundary), Intersection
16. Higher Order Components (HOC)
17. Event Delegation
18. State Lifting (Child to Parent)
19. Why TS?

JavaScript:
1. let, const, var
2. How JavaScript is single-threaded
3. Execution context
4. Placement of Script tag: async vs defer
5. How one thread handles many synchronous and asynchronous operations
6. Types of for loops
7. Web API: Task and Microtask Queue
8. Temporal Dead Zone (TDZ) and hoisting
9. Closure and lexical scope
10. Currying
11. Every ES6 feature
12. Higher-Order Functions (HOF)
13. Exception Handling
14. this keyword
15. call, bind, apply
16. Prototypes, Polyfills and Classes
17. Callbacks, Promises and Async/Await
18. Objects and Arrays: Methods
19. DOM
20. Shallow vs Deep Copy

Java:
1. Type of language
2. JDK, JVM, JRE
3. Stack and heap
4. OOP pillars
5. Immutability
6. Wrapper Classes, Autoboxing and Unboxing
7. Upcast and Downcast
8. Abstract classes and interfaces
9. Method overloading and overriding
10. Diamond Problem
11. Enums
12. Copy constructor
13. Exception handling and hierarchy, propagation
14. final, finally, and finalize
15. throw vs throws
16. equals vs ==
17. static and static block
18. Instance block
19. Lambda expressions
20. Comparator vs Comparable
21. Collections
22. Multithreading
23. Stream API
24. Map, Filter, Reduce

C++:
1. C vs C++
2. Why C/C++ is between high and low level (mid-level)
3. Pointers, References and Smart Pointers
4. 1D and 2D array pointer initialization
5. Stack and heap
6. OOPS
7. Virtual classes, methods, destructor
8. Abstract classes/Interface/Pure Virtual Classes
9. Method overloading and overriding, Operator Overloading
10. Friend function and class
11. Diamond problem fix
12. Copy constructor
13. Exception handling
14. Generics, Templates and STL
15. Lambda, Const and Mutable
16. Comparator
17. Struct, enums, and unions

SQL:
1. Type of language
2. DDL, DML, DCL, TCL, DQL
3. Drop vs delete vs truncate
4. Alter DDL
5. Sequence of SQL commands
6. Keys and Constraints
7. Wildcard operators (pattern matching)
8. Joins
9. Subquery, Nested Subquery, Correlated Subquery
10. Group by, having, order by
11. Nth Highest Salary, Limit
12. Window Functions
13. Views, Stored Procedure, Triggers
14. ACID properties