Hey everyone,
I was going through interview experiences on LeetCode and found a really detailed post covering interviews from multiple top companies (Amex, PayPal, Paytm, UKG, Walmart, NetApp, Goldman Sachs, etc.).

I extracted and compiled the most important questions asked — categorized into DSA and Development/System Design/Core Java.
Thought it might help others preparing for Backend/Java roles.
Here it goes 👇

✅ DSA QUESTIONS (with Company Names)

Array / String / Searching

• Two Sum (Virgin Pulse)

• Find minimum in a rotated sorted array (Virgin Pulse)

• Sort array in one pass (0,1,2 sorting) (NetApp)

• Rotate matrix by 90 degrees (Paytm)

• Array & string manipulation questions (Walmart)

• Valid Parenthesis (Walmart)

• Check if number is power of 10 — recursion (Goldman Sachs)

• Mathematics-based DSA question (Goldman Sachs)

• Course Schedule — OA (NetApp)

• Medium/Hard DSA OA questions (PayPay)

• OA with MCQs + coding (Paytm)

• Debug + Git + DSA (OA) (UKG)

• Medium OA DSA (Walmart)

Linked List

• Reorder linked list: 1→7→2→6→3→5→4 (NetApp)

• Merge n linked lists (Goldman Sachs)

Tree / Graph / Recursion / DP

• Left View of Binary Tree (PayPay)

• LCS (DP) (NetApp)

• House Robber (Walmart)

• Tower of Hanoi (Goldman Sachs)

DEVELOPMENT / BACKEND / SYSTEM DESIGN QUESTIONS (with Company Names)

1. Core Java

HashMap internal working (Virgin Pulse / Goldman Sachs)

HashMap from scratch (Virgin Pulse / Goldman Sachs)

Singleton pattern (Virgin Pulse)

Priority Queue from scratch (Goldman Sachs)

Multithreading concepts (Virgin Pulse / Walmart / Paytm)

ExecutorService implementations (Virgin Pulse)

Concurrency + Synchronization (Paytm)

Java 8 vs 11 vs 17 (Paytm)

OOP, exceptions, collections (Almost all companies)

2. Spring Boot / Microservices

Spring vs Spring Boot (UKG)

REST API basics (UKG / Walmart)

Spring Boot annotations (UKG)

Microservice vs Monolith (Amex)

Controller LLD (Walmart)

Exception handling in Spring Boot (Walmart)

API response codes (Walmart)

Automating API jobs / schedulers (Walmart)

3. System Design (HLD + LLD)

Scale from 1 req/sec → 10,000 req/sec globally (UKG)

Design review/rating system (Amazon/Flipkart style) (UKG)

CDN — what & why (Amex)

Caching — usage + need (Amex)

CI/CD & deployments (UKG / Walmart)

REST architecture LLD (NetApp)

Payment settlement LLD (Paytm)

Vertical vs Horizontal scaling (Walmart)

Architecture of your current project (PayPay / NetApp)

Why Postgres over MongoDB (PayPay)

What design changes you'd make in your project (NetApp)

4. Database / SQL

SQL joins, grouping, filters (Amex / UKG / PayPay / Walmart)

Indexing (Walmart / Paytm)

Normalization (Walmart)

Hashing (Paytm)

MongoDB vs Postgres (PayPay)

Sorting custom objects (Comparator) (Goldman Sachs)

5. Cloud / DevOps / Infra

Docker basics (Amex / UKG / Paytm)

Kubernetes (pods, ingress, services) (UKG / Paytm / Walmart)

Kafka deep dive (Paytm)

Azure basics (Paytm)

ELK Stack (Paytm)

Git & Version control (UKG / Paytm)

SonarQube (UKG)

TCP configs (Walmart)

6. Resume-Based / Managerial

Resume walkthrough (All companies)

Tech stack + architecture deep dive (PayPay / NetApp / Walmart)

Why switch? Expected CTC? (Amex / UKG)

Why relocate? (UKG)

Situational questions (UKG / NetApp / Goldman Sachs)

Detailed project discussions (All companies)