jayanth ilavarasan

💡 Java Backend Developer (3+ Yrs) :: Interview Questions Asked @ Amazon 🚀 ♦️ Core Java (OOPs, Collections, Concurrency) 1️⃣ Explain the internal working of ConcurrentHashMap in Java 8. 2️⃣ Difference between synchronized, ReentrantLock and ReadWriteLock. 3️⃣ How does Java handle memory leaks and how would you detect them? 4️⃣ How would you design a thread-safe singleton in Java? 5️⃣ Explain Java memory model (heap, stack, metaspace) and garbage collection tuning. ♦️ Spring & Spring Boot 6️⃣ Explain how dependency injection works internally in Spring. 7️⃣ Difference between Spring Boot starters vs manual dependency management. 8️⃣ How do you implement idempotency in REST APIs? 9️⃣ How do you handle huge traffic in Spring Boot APIs? (connection pool, caching, async calls) 🔟 How would you secure AWS-hosted Spring Boot APIs with IAM roles / Cognito / JWT? ♦️ JPA / Hibernate 1️⃣1️⃣ How would you optimize large batch inserts/updates in Hibernate? 1️⃣2️⃣ Explain difference between entity graphs and fetch joins for optimizing queries. 1️⃣3️⃣ How does 2nd level caching work in Hibernate and which providers have you used? 1️⃣4️⃣ How to handle optimistic locking failures gracefully? 1️⃣5️⃣ How do you tune SQL queries generated by JPA for performance? ♦️ Microservices & Architecture 1️⃣6️⃣ Explain the difference between orchestration and choreography in microservices. 1️⃣7️⃣ How would you handle distributed transactions at scale? (Saga / Outbox pattern) 1️⃣8️⃣ Explain API throttling, rate limiting, and request bursting. 1️⃣9️⃣ How do you design a high-availability, fault-tolerant microservice? 2️⃣0️⃣ Describe an event-driven architecture you have implemented (Kafka, SQS, SNS, etc.). ♦️ Cloud & DevOps Basics (AWS Focus) 2️⃣1️⃣ Explain difference between AWS EC2, ECS, EKS, and Lambda. 2️⃣2️⃣ How would you secure secrets and credentials in AWS? (Parameter Store, Secrets Manager) 2️⃣3️⃣ How do you achieve blue/green or canary deployments on AWS? 2️⃣4️⃣ How do you implement logging, tracing and monitoring (CloudWatch, X-Ray, ELK)? 2️⃣5️⃣ Difference between scaling using Auto Scaling Groups vs Kubernetes HPA. ♦️ DSA & System Design (Amazon Special Focus) 2️⃣6️⃣ Design a rate limiter (like Amazon API Gateway throttling). 2️⃣7️⃣ Design a cache system with expiration and eviction policy. 2️⃣8️⃣ Given a massive log file stored in S3, find top 10 frequently accessed URLs efficiently. 2️⃣9️⃣ Given two sorted streams of data, merge them in real-time with minimal memory. 3️⃣0️⃣ Implement a thread-safe LRU cache in Java. ♦️ Behavioral / Leadership Principles (Always Asked at Amazon) 3️⃣1️⃣ Tell me about a time you disagreed with your manager. 3️⃣2️⃣ Describe a situation where you delivered results under tight deadlines. 3️⃣3️⃣ Tell me about a time when you improved a process or system. 3️⃣4️⃣ Describe how you handle failure in a project. 3️⃣5️⃣ Tell me about a time when you influenced a team without authority

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🚀 Java Developer Interview Prep: Recently Asked Questions! Cracking interviews isn’t just about coding — it’s about clarity of concepts. Here are some real interview questions I recently came across: 💡 Core Java & OOP JDK vs JRE vs JVM Multiple Inheritance in Java — why not supported with classes? Garbage Collector — how it works under the hood equals() vs == Singleton & Factory Design Patterns 💡 Java 8 & Collections Features of Java 8 (Streams, Functional Interfaces, Lambda) Comparable vs Comparator Stream API: findFirst() vs findAny() HashMap internal working & how to make it thread-safe ArrayList vs Vector vs ConcurrentHashSet 💡 Problem Solving Find Armstrong Numbers Two-Sum problem (Java 8 Stream solution) Count occurrences of characters in a String Max number using Java Streams Insertion Sort vs Bubble Sort (Time Complexity difference) 💡 Spring Boot & Microservices What is Spring Boot Starter? Role of IoC & Dependency Injection @ComponentScan, @Qualifier, @Transactional, @Controller How JWT Tokens secure microservices Spring Boot Component architecture 💡 SQL Types of Joins (focus on LEFT OUTER JOIN) Indexing & Types of Indexing WHERE vs GROUP BY Views and their use cases 🔑 Preparation is the key — interviews test both your fundamentals & your problem-solving skills. #JavaInterviewPrep #SpringBoot #Microservices #SQL #InterviewTips #BackendDevelopment #JavaDevelopers #Coding

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Hi Everyone 👋, I appeared for a few Java Developer interviews for roles in the 2–4 years experience range. Some interviews went well, some were learning experiences — but one thing was clear: Most companies ask questions from a few common topics. So I thought of putting everything together here — this might help someone who's currently preparing. 👇 JAVA - 1. OOPS 2. Collections 3. Exception Handling 4. Java 8 5. Thread 6. String 7. Design Patterns 8. Memory Management 9. Constructors & other fundamentals 10. Coding (Java 8, Array, String, Linked List) SPRING BOOT - 1. Basics & Annotations 2. Project Structure 3. Exception Handling 4. Spring Boot Properties 5. Testing MICROSERVICES 1. Basics & Key Differences 2. Communication Between Services 3. Load Balancing 4. API Gateway 5. Design Patterns OTHER TOPICS 1. SQL (Theory & Coding) 2. Spring MVC, Spring Security 3. Hibernate 4. Git, Bitbucket, Maven, Jenkins, Docker 5. Project Specific ❤️ If you found it helpful, give it a like. 🤝 Feel free to connect and share your own experiences. ✨ Let’s connect and learn from each other. ⭐ Good luck to everyone preparing out there! #InterviewTips #JobSearch #DSA #SQL #SystemDesign #CareerGrowth #TechInterviews #LinkedInCommunity #Java #JavaDeveloper #JavaBackend

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🚀 Roadmap to Master Java DSA (specifically for Product-Based MNCs) 👉 Whether you’re a fresher or have 10+ years of experience, one thing is constant: If you want to break into top product companies (0–15 yrs exp) → DSA is your entry ticket. Yes, you’ll need other skills too (Springboot,System Design, Databases, Cloud, etc.), but DSA is the door that opens the playground. Here’s a structured roadmap you can follow (language doesn’t matter, concepts are universal 👇): ⸻ 🛠 Step 1: Programming Foundations ✅ Master 1 language (Java / C++ / Python) ✅ OOP (Encapsulation, Inheritance, Polymorphism, Abstraction) ✅ Strings & basic problems ⸻ 📊 Step 2: Complexity Analysis ✅ Big-O, Big-Theta, Big-Omega ✅ Time vs Space trade-offs ✅ Common pitfalls in nested loops ⸻ 🔢 Step 3: Arrays & Strings ✅ Prefix Sum, Sliding Window ✅ Binary Search (and its advanced variations) ✅ Sorting (Quick, Merge, Counting) ✅ String patterns (Anagrams, Substrings, KMP) ⸻ 🔄 Step 4: Recursion & Backtracking ✅ Factorial, Fibonacci, Power ✅ N-Queens, Sudoku Solver, Subsets/Permutations ⸻ 🔗 Step 5: Linked List ✅ Insert, Delete, Reverse ✅ Detect cycle, Merge sorted lists ⸻ 📚 Step 6: Stack & Queue ✅ Next Greater Element ✅ Min Stack ✅ Sliding Window Maximum ⸻ 🔑 Step 7: Hashing ✅ HashMap, HashSet ✅ Two Sum, Longest Substring Without Repeat ⸻ 🌳 Step 8: Trees & BST ✅ Traversals (Inorder, Preorder, Postorder, Level Order) ✅ Height, Diameter, LCA ✅ BST operations ⸻ ⛰ Step 9: Heaps & Priority Queue ✅ Heapify, Heap Sort ✅ Kth largest element, Top-K problems ⸻ 🌐 Step 10: Graphs ✅ BFS, DFS ✅ Dijkstra, Bellman-Ford ✅ Kruskal’s & Prim’s (MST) ✅ Topological Sort, Cycle Detection ⸻ 🧩 Step 11: Dynamic Programming (DP) ✅ Fibonacci, Knapsack ✅ LCS, LIS ✅ DP on Grids & Strings ✅ Palindromes, Edit Distance ⸻ 🎯 Step 12: Practice & Mock Interviews ✅ 300–400 problems across patterns ✅ Focus on problem-solving mindset ✅ Do timed mock interviews ⸻ ⚡ Suggested Timeline ✅ 3–4 months → Strong foundation ✅ 6–8 months → Interview-ready ⸻ 📌 Final Thoughts ✅ DSA is not just about coding — it’s about how you think. ✅ It’s the foundation of every great developer. ✅ Once you master it, you can move confidently into System Design, Microservices, Cloud, and Architecture. ⸻ 💡 Which step are you currently at in your DSA journey? 👇 Drop a comment, let’s discuss! #DSA #Java #CodingInterviews #Roadmap #SystemDesign #100DaysOfCode #StriversSheet #NeetCode #LeetCode #GeeksforGeeks #Developers #Learning

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✨ Sharing My Interview Journey ✨ A few days ago, I appeared for an interview for the API Developer position. The interview process tested my knowledge of Java/Spring Boot, Hibernate, Microservices, problem-solving abilities. ## Round 1 ## ---------------------------------------------------------------- 1. What is a wrapper class? 2. Difference between heap and stack memory? 3. Difference between interface and abstract class 4. Java 8 features 5. Can a functional interface inherit another interface? 6. What is Git? How do you use it in your project? 7. What is Hystrix? 8. What is API Gateway? Responsibility of that. 9. What is Circuit Breaker pattern? 10. Advantages of Spring Boot. 11. What is Actuator? 12. What is dependency injection? 13. What is setter and constructor injection? 14. Second largest number from an array 15. String palindrome 16. How do you secure code? 17. How can you set validity for a token? 18. JWT 19. How do you validate the token? 20. Spring annotations 21. What is Stream in Java? Explain any of its methods in detail. ## Round 2 ## ---------------------------------------------------------------- 1. Difference between @Component and @Service 2. Is a service internally a component or not? 3. What are service and repository classes? 4. Is HashMap thread-safe? Thread-safe version? 5. Do we have to write a method in a repo or not? 6. If we want to write a complex query, then how can we write it using a repo? 7. If two keys get the same hash code, then what? 8. Difference between @Controller and @RestController 9. Difference between Spring and Spring Boot 10. Version of Spring Boot and Spring used in the project. 11. First-level and second-level caching I’m sharing this to help others who might be preparing for similar interviews. Happy Learning!!!😀

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Interview Experience #radiancetechnologies I would like to share the interview questions that were asked in my technical round. Hope this helps professionals who are preparing for Java/Spring Boot interviews. 🚀 🔹 Interview Questions: 1. Explain the project you have worked on. 2. Which Java version have you used? 3. Which Spring Boot version have you used? 4. Which design patterns have you implemented? 5. What does IOC mean? 6. How do you inject dependencies in software? 7. Have you worked with Singleton classes? Explain. 8. A list contains duplicate integers. Fetch the top 3 distinct marks. (Example: [78, 90, 92, 78, 99, 88, 99]) 9. Which database are you working with? 10. Write a query to find the second-highest salary of employees. 11. Write the same query using LIMIT and OFFSET. 12. Which authentication method have you used in your project? 13. What is JWT? 14. What is a Functional Interface? 15. What is AWS Lambda? ✨ Key Takeaway: Be confident with Core Java, Spring Boot, SQL, Authentication methods, and AWS basics. 📌 Sharing this to help the community and also keep my own preparation strong. #Java #SpringBoot #SQL #Microservices #InterviewPreparation #CareerGrowth #AWS

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📌 Day 53 of #60DaysOfJava – Java Interview Question #3 (Collections) ⸻ 💡 Interview Question: 👉 What is the difference between HashMap and HashTable in Java? 🔑 Answer: HashMap • Allows one null key & multiple null values • Not synchronized → faster in single-threaded apps • Introduced in Java 1.2 • Widely used in modern applications HashTable • No null keys or values allowed • Synchronized → thread-safe but slower • Legacy (Java 1.0) • Rarely used today; replaced by ConcurrentHashMap ⚡ Tip for interviews: If asked about thread safety, always mention that ConcurrentHashMap is the better choice than HashTable. #Java #Collections #HashMap #HashTable #InterviewPrep #60DaysOfJava

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💼 Interview Series #Day1 👨‍💻 Interviewer: "final, finally, and finalize() — are they the same or not?" ✅ Answer: In Java, they’re totally different concepts: 🔹 final → makes a variable constant or a reference unchangeable (can’t reassign). Also used with classes (can’t be extended) and methods (can’t be overridden). 🔹 finally → a block in try-catch that always runs, whether an exception occurs or not. 🔹 finalize() → a method once used for cleanup before GC. Deprecated — avoid using in modern Java. 💡 Takeaway: Same prefix, totally different purposes. Mastering these will make your code safer and cleaner. 𝗙𝗶𝗻𝗱 𝗶𝘁 𝗛𝗲𝗹𝗽𝗳𝘂𝗹? Be the part of interview series, and follow Paras Gupta, and feel free to share more interview questions in the comments! 🙌 Learn and Grow together. 🤝 #Java #JavaInterview #CodingTips #InterviewPreparation #JavaDeveloper #TechTips #JavaLearning #ProgrammingTips #CodeBetter #JavaConcepts #BackendDeveloper #JavaCoding

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💡 Java Backend Developer (3+ Yrs) :: Interview Questions Asked @ Capgemini ♦️ Core Java (OOPs, Collections, Concurrency Basics) 1️⃣ Explain difference between abstraction and encapsulation with examples. 2️⃣ How does ConcurrentHashMap differ from HashMap? 3️⃣ Difference between equals() and == in Java. 4️⃣ What is the difference between wait(), sleep(), and join()? 5️⃣ Explain thread safety and how to achieve it in Java. ♦️ Spring & Spring Boot 6️⃣ What is the difference between Spring MVC and Spring WebFlux? 7️⃣ Explain @Component, @Service, @Repository annotations. 8️⃣ How do you create and use custom annotations in Spring? 9️⃣ What is the difference between @RestController and @Controller? 🔟 How do you secure REST APIs in Spring Boot (JWT/OAuth2)? ♦️ JPA / Hibernate 1️⃣1️⃣ Difference between get() and load() in Hibernate. 1️⃣2️⃣ How does caching work in Hibernate (1st level, 2nd level)? 1️⃣3️⃣ What is N+1 select problem in JPA and how do you fix it? 1️⃣4️⃣ Explain difference between CascadeType.ALL and CascadeType.MERGE. 1️⃣5️⃣ How does dirty checking work in Hibernate? ♦️ Microservices & Architecture 1️⃣6️⃣ How do services communicate in microservices (REST, gRPC, Messaging)? 1️⃣7️⃣ Explain role of Kafka/RabbitMQ in microservices. 1️⃣8️⃣ What is API versioning and why is it important? 1️⃣9️⃣ How do you achieve distributed logging in microservices? 2️⃣0️⃣ Explain eventual consistency in distributed systems with example. ♦️ Cloud & DevOps Basics 2️⃣1️⃣ What is the difference between AWS S3 and RDS? 2️⃣2️⃣ How do you use Docker Compose in projects? 2️⃣3️⃣ What is the difference between Blue-Green and Rolling deployments? 2️⃣4️⃣ How does Kubernetes handle scaling and self-healing? 2️⃣5️⃣ How do you secure secrets in CI/CD pipelines?

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