General Software Engineer Interviews: Technical Depth & Career Progression 2026

1. 1. What's the difference between == and === in JavaScript?

   == compares values with type coercion, === compares values and types without coercion

2. 2. Explain the difference between let, const, and var.

   Scope differences: var (function-scoped), let/const (block-scoped), const is immutable

3. 3. What is closure in JavaScript? Give an example.

   Function that retains access to outer scope variables even after outer function returns

4. 4. How does the 'this' keyword work in JavaScript?

   Context depends on how function is called: global, object method, constructor, or explicit binding

5. 5. What's the difference between null and undefined?

   undefined: declared but not assigned; null: intentionally assigned empty value

1. 6. Explain event bubbling and capturing in DOM.

   Event propagation phases: capturing (top-down) and bubbling (bottom-up)

2. 7. How do you handle asynchronous operations in JavaScript?

   Callbacks, Promises, async/await - evolution of async programming

3. 8. What are higher-order functions? Give examples.

   Functions that take other functions as arguments or return functions: map, filter, reduce

4. 9. Explain prototype inheritance in JavaScript.

   Objects inherit properties/methods from prototype chain

5. 10. How does garbage collection work in JavaScript?

   Automatic memory management using mark-and-sweep algorithm

1. 11. How would you implement debouncing and throttling?

   Performance optimization techniques for limiting function execution frequency

2. 12. Explain Web Workers and when you'd use them.

   Background threads for CPU-intensive tasks without blocking main thread

3. 13. How do you optimize JavaScript performance?

   Code splitting, lazy loading, memoization, avoiding memory leaks

4. 14. What's the difference between deep and shallow copying?

   Shallow: copy references; Deep: copy nested objects/arrays completely

5. 15. How would you implement a custom Promise?

   Understanding Promise internals: states, handlers, chaining

1. 16. What's the difference between Array and Object in JavaScript?

   Arrays: ordered, indexed; Objects: key-value pairs, unordered

2. 17. How do you reverse a string without using built-in methods?

   Loop backward or use recursion to build reversed string

3. 18. Find the largest number in an array.

   Math.max(), reduce(), or loop comparison

4. 19. Check if a string is a palindrome.

   Compare string with its reverse, accounting for case and spaces

5. 20. Remove duplicates from an array.

   Set, filter with indexOf, or reduce approaches

1. 21. Implement a binary search algorithm.

   O(log n) search in sorted array using divide-and-conquer

2. 22. What's the time complexity of common Array methods?

   push/pop: O(1), shift/unshift: O(n), indexOf: O(n), sort: O(n log n)

3. 23. Implement a function to flatten a nested array.

   Recursive approach or iterative with stack

4. 24. How do you detect a cycle in a linked list?

   Floyd's cycle detection (tortoise and hare)

5. 25. Implement a stack using arrays.

   LIFO principle with push/pop operations

1. 26. Implement a LRU (Least Recently Used) cache.

   HashMap + Doubly LinkedList for O(1) operations

2. 27. How would you implement a trie data structure?

   Tree structure for efficient string operations and autocomplete

3. 28. Solve the "Two Sum" problem in optimal time.

   HashMap to store complements for O(n) solution

4. 29. Implement merge sort algorithm.

   Divide-and-conquer sorting with O(n log n) complexity

5. 30. How do you find the kth largest element in an array?

   Quickselect algorithm or min-heap approach

1. 31. What's the difference between frontend and backend?

   Client-side vs server-side responsibilities and technologies

2. 32. Explain how HTTP requests work.

   Request/response cycle, methods (GET, POST, etc.), status codes

3. 33. What's the difference between REST and GraphQL?

   API design philosophies: multiple endpoints vs single endpoint with flexible queries

4. 34. How do you handle form validation in web applications?

   Client-side and server-side validation strategies

5. 35. What's the purpose of a database index?

   Improve query performance by creating sorted references

1. 36. How would you design a URL shortener like bit.ly?

   Base62 encoding, database schema, caching strategies

2. 37. Explain caching strategies and when to use each.

   Browser, CDN, application, database caching

3. 38. How do you handle database scaling?

   Vertical vs horizontal scaling, read replicas, sharding

4. 39. What's the difference between SQL and NoSQL databases?

   Structure, scalability, consistency, and use cases

5. 40. How would you implement real-time notifications?

   WebSockets, Server-Sent Events, or push notifications

1. 41. Explain React component lifecycle methods.

   Mounting, updating, unmounting phases and hooks equivalent

2. 42. What's the difference between state and props in React?

   Internal component data vs data passed from parent

3. 43. How do you optimize React app performance?

   Memoization, code splitting, lazy loading, profiling

4. 44. Explain the purpose of package.json in Node.js.

   Project metadata, dependencies, scripts configuration

5. 45. How do you handle environment variables in applications?

   .env files, process.env, security considerations

6. 46. What's the difference between unit and integration testing?

   Testing individual components vs component interactions

7. 47. Explain Git workflow and common commands.

   Branching, merging, conflict resolution strategies

8. 48. How do you deploy a web application?

   Build process, hosting options, CI/CD pipelines

9. 49. What's Docker and when would you use it?

   Containerization for consistent environments and deployment

10. 50. How do you ensure application security?

    Input validation, authentication, HTTPS, dependency updates

The Think-Aloud Strategy

Most candidates fail technical interviews not because they can't solve the problem, but because the interviewer can't follow their thought process. Here's how to fix that:

1. 1. Clarify the problem: "Just to confirm, are we looking for..."
2. 2. Discuss edge cases: "What should happen if the input is empty?"
3. 3. Outline your approach: "I'm thinking we could use X because..."
4. 4. Start with brute force: "The naive solution would be..."
5. 5. Optimize iteratively: "We can improve this by..."
6. 6. Test your solution: "Let me walk through an example..."

Language-Specific Preparation