Java/Spring Boot interview questions shared by a professional.

🔥 Spring Boot Interview Scenario You Must Know! One of the most common real-world interview questions in Java + Microservices interviews is: 👉 “How do you trace a single request across multiple microservices in production?” This question tests your knowledge of: ✅ Distributed tracing ✅ Correlation IDs ✅ Tools like Sleuth, Zipkin, or OpenTelemetry 💡 Answer Tip: You trace a request across services using a Correlation ID that travels along with the request in every upstream & downstream call. Frameworks like Spring Cloud Sleuth automatically generate these IDs and integrate seamlessly with Zipkin/Jaeger for visualization. 🎯 Why this matters in interviews? Because companies want to know if you can handle production-grade issues like debugging latency, bottlenecks, and failures in a microservices environment. 📌 Save this post, practice this explanation, and be ready to stand out in interviews. #SpringBoot #JavaDeveloper #Microservices #SystemDesign #BackendDevelopment #TechInterviews #JavaCoding #InterviewTips #DistributedSystems #CloudNative

💡 Interview Experience – Questions I Faced Recently, I attended an interview where I was asked a mix of Java, Spring Boot, Kafka, SQL questions. Sharing them here so it might help others preparing 👇 Interview Questions 1️⃣ What is rate limiting and how do you implement rate limiting in your application? 2️⃣ Suppose a producer sends a huge amount of data to a topic, how can the consumer read/process the data efficiently? 3️⃣ Why did you use Kafka when AWS SNS and RabbitMQ are also available? 4️⃣ Why are you looking for a job change? 5️⃣ What challenges have you faced in your project and how did you handle them? 6️⃣ How did you implement pagination in your project? How do OFFSET and LIMIT work in SQL, and if you want to go to the last page, what would be your query? 7️⃣ What is serialization, and how are Java objects serialized and deserialized? 8️⃣ What is the difference between Set and HashSet? 9️⃣ What is flatMap and how is it different from map in Java streams? 🔟 What are the different bean scopes in Spring? 1️⃣1️⃣ What is the purpose of equals() and hashCode() methods, and how do they work? 1️⃣2️⃣ What is the internal working of HashSet? 1️⃣3️⃣ What is an API Gateway and why is it used? 1️⃣4️⃣ How do you implement security in a Spring Boot application? 1️⃣5️⃣ Can we inject a singleton bean into a prototype bean class in Spring? 1️⃣6️⃣ Write a program to sort Employee objects using firstName, and if firstName is the same, then sort by lastName. ✅ These are real questions I faced in one interview session. 💬 Hope this helps others who are preparing. Feel free to share your thoughts or how you would approach these! #Java #SpringBoot #Kafka #Microservices #SQL #InterviewPreparation #SystemDesign

Preparing for Java Software Engineer interviews? 👉 You need depth in Core Java + Spring + SQL + System Design, and the ability to explain trade-offs with real project scenarios. Here’s a curated roadmap of interview questions that top product companies love to ask: 𝗖𝗼𝗿𝗲 𝗝𝗮𝘃𝗮 • Difference between HashMap, HashTable, and ConcurrentHashMap • How does Garbage Collection work in JVM? • Explain volatile and synchronized in multithreading • Deep copy vs Shallow copy • How does the Java memory model work (Heap, Stack, Metaspace)? 𝗦𝗽𝗿𝗶𝗻𝗴 & 𝗦𝗽𝗿𝗶𝗻𝗴 𝗕𝗼𝗼𝘁 • What is Dependency Injection? How does Spring handle it internally? • Difference between @Component, @Service, and @Repository • How does Spring Boot auto-configuration work? • Exception handling best practices in REST APIs • How to secure REST APIs (JWT, OAuth2)? 𝗝𝗣𝗔 / 𝗛𝗶𝗯𝗲𝗿𝗻𝗮𝘁𝗲 • Difference between Lazy and Eager loading • What are N+1 query problems? How to solve them? • How does Hibernate manage transactions? • Entity lifecycle states (Transient, Persistent, Detached, Removed) 𝗦𝗤𝗟 & 𝗗𝗮𝘁𝗮𝗯𝗮𝘀𝗲 • Write a query to find the 2nd highest salary from Employee table • Difference between INNER JOIN, LEFT JOIN, RIGHT JOIN • What are indexes? Clustered vs Non-clustered • How to optimize slow queries? 𝗗𝗦𝗔 / 𝗣𝗿𝗼𝗯𝗹𝗲𝗺 𝗦𝗼𝗹𝘃𝗶𝗻𝗴 • Implement LRU Cache • Detect a cycle in a linked list • Find longest substring without repeating characters • Merge overlapping intervals • Design a rate limiter 𝗦𝘆𝘀𝘁𝗲𝗺 𝗗𝗲𝘀𝗶𝗴𝗻 • Design a URL Shortener like bit.ly • How would you scale a notification service? • Difference between Monolith vs Microservices • Use of API Gateway and Load Balancer • CAP Theorem explanation with real-world examples 💡 Pro tip: Don’t just prepare answers — be ready to explain trade-offs and real project use cases. #Java #SpringBoot #SQL #SystemDesign #Interviews #FullStack #Career

💡 Spring Boot Interview Prep! ☕🔥 If you’re a Java dev and haven’t been grilled on Spring Boot yet… just wait 😅 (Trust me, the questions come faster than a NullPointerException in production). That’s why I pulled together the most important Spring Boot topics you must master before your next interview: 🚀 Core Topics You Can’t Skip: Spring Boot Basics (Starters, Annotations, Auto-Config) REST APIs (@RestController, @RequestBody, HTTP methods) Spring Data JPA & Transactions Security (JWT, OAuth2, CSRF — the fun stuff 🔒) Messaging (Kafka, RabbitMQ) Reactive Programming (WebFlux, Mono, Flux) Spring Cloud (Eureka, Config, Gateway, Circuit Breaker) Monitoring & Deployments (Docker, WAR packaging, Cloud integration) 👉 The detailed Q&A guide is in a PDF (for serious prep). But here’s the reminder: Spring Boot isn’t just a framework, it’s the cheat code for modern Java devs. ⚡ Whether you’re building APIs, microservices, or cloud-native apps, Spring Boot is what keeps Java relevant in 2025. 😂 Fun Fact: 90% of interviews start with “So… what is Spring Boot and why do we use it?” → And if you freeze there, you’ll wish you had a Circuit Breaker IRL. 💬 Curious? Drop a comment ⬇️ #SpringBoot #Java #Microservices #SpringFramework #InterviewPreparation #CloudNative #BackendDevelopment

📌 Java & Spring Boot Interview Questions to Revisit Recently, I came across some interesting questions that are frequently asked in technical interviews. Thought of sharing them here so they can help anyone preparing or revising concepts 🚀 🔹 Questions: 1️⃣ How does HashMap work internally? 2️⃣ Difference between @Component, @Service, and @Repository. 3️⃣ Write a method to find the first non-repeating character in a string. 4️⃣ Difference between synchronous and asynchronous communication. 5️⃣ Difference between monolithic and microservices architecture. 6️⃣ Difference between lazy loading and eager loading. 7️⃣ Difference between @Mock and @MockBean. 8️⃣ Explain rule-based Spring Security. 9️⃣ How does auto-configuration work in Spring Boot? 🔟 Difference between intermediate and terminal operations in Stream API. 1️⃣1️⃣ How does the Java Memory Model work? 1️⃣2️⃣ Explain @SpringBootApplication annotation. 1️⃣3️⃣ Explain functional interfaces. 1️⃣4️⃣ Explain API Gateway, service registration, and discovery. 💡 These are core concepts—great for brushing up, whether you’re preparing for interviews or strengthening your daily development knowledge. 👉 Which of these do you find most challenging? 👉 How many can you confidently answer on the spot? Let’s share and learn together ⬇️ #Java #SpringBoot #Microservices #SoftwareEngineering #SystemDesign #InterviewPreparation #BackendDevelopment #Coding #TechCareers #LearningTogether

I reviewed 100+ Java developer interviews. These 5 Spring Boot questions eliminated almost 80% of candidates. It wasn't about tricky, obscure problems. The deal-breakers were almost always on fundamental yet powerful concepts that everyone thinks they know. 😮💨 I've compiled the most critical questions. The ones that truly separate prepared candidates from the rest into a complete guide: "The Top 30 Spring Boot Interview Questions (2025 Edition)." This isn't just a list. It's a deep dive into: ✅ The "why" behind the answers – not just the "what." ✅ Common pitfalls interviewers watch out for. ✅ Advanced concepts that demonstrate real-world experience. Whether you're prepping for your next interview or looking to strengthen your team, this guide has you covered. 🔗 Get the full list of questions and detailed answers here: https://lnkd.in/dhuskFyd What's the one Spring Boot question you've found to be the most revealing in an interview? Share below! 👇 #SpringBoot #Java #InterviewTips #SoftwareEngineering #BackendDevelopment #Coding #TechJobs #Developer #CareerGrowth #Programming

🌱 Spring Boot Interview Questions — For Backend & Full-Stack Java Devs! ☕️ If you're preparing for interviews that involve Java + Spring Boot, I’ve compiled a practical PDF guide of frequently asked Spring Boot questions, ideal for quick revision and last-minute prep. 📘 What you’ll find inside: ✅ Spring Boot basics & auto-configuration ✅ Differences between Spring & Spring Boot ✅ RESTful web services, annotations, starters, and beans ✅ JPA, H2, Actuator, and DevTools ✅ Dependency Injection, Component Scan, and Microservices ✅ Real-world architecture questions and diagrams ✅ Advanced topics like caching, exception handling, profiles, and REST versioning Whether you're a Java backend dev, a full-stack engineer, or just curious about microservice architecture, this PDF is packed with the right questions to boost your confidence before an interview. #springboot #java #microservices #backenddevelopment #fullstack #javainterview #softwareengineer #springframework #interviewprep #techcareers

🌱 Spring Boot Interview Questions — For Backend & Full-Stack Java Devs! ☕️ If you're preparing for interviews that involve Java + Spring Boot, I’ve compiled a practical PDF guide of frequently asked Spring Boot questions, ideal for quick revision and last-minute prep. 📘 What you’ll find inside: ✅ Spring Boot basics & auto-configuration ✅ Differences between Spring & Spring Boot ✅ RESTful web services, annotations, starters, and beans ✅ JPA, H2, Actuator, and DevTools ✅ Dependency Injection, Component Scan, and Microservices ✅ Real-world architecture questions and diagrams ✅ Advanced topics like caching, exception handling, profiles, and REST versioning Whether you're a Java backend dev, a full-stack engineer, or just curious about microservice architecture, this PDF is packed with the right questions to boost your confidence before an interview. #springboot #java #microservices #backenddevelopment #fullstack #javainterview #softwareengineer #springframework #interviewprep #techcareers

🌱 Spring Boot Interview Questions — For Backend & Full-Stack Java Devs! ☕️ If you're preparing for interviews that involve Java + Spring Boot, I’ve compiled a practical PDF guide of frequently asked Spring Boot questions, ideal for quick revision and last-minute prep. 📘 What you’ll find inside: ✅ Spring Boot basics & auto-configuration ✅ Differences between Spring & Spring Boot ✅ RESTful web services, annotations, starters, and beans ✅ JPA, H2, Actuator, and DevTools ✅ Dependency Injection, Component Scan, and Microservices ✅ Real-world architecture questions and diagrams ✅ Advanced topics like caching, exception handling, profiles, and REST versioning Whether you're a Java backend dev, a full-stack engineer, or just curious about microservice architecture, this PDF is packed with the right questions to boost your confidence before an interview. #springboot #java #microservices #backenddevelopment #fullstack #javainterview #softwareengineer #springframework #interviewprep #techcareers

🚀 Spring Boot Interview Questions – For Backend & Full-Stack Java Devs! If you’re preparing for interviews involving Java + Spring Boot, this guide is a game-changer. I’ve compiled a practical PDF covering frequently asked Spring Boot questions — perfect for last-minute revision and interview confidence. 📌 What’s inside the PDF? ✅ Spring Boot basics & auto-configuration ✅ Spring vs. Spring Boot (key differences) ✅ RESTful web services, annotations, starters & beans ✅ JPA, H2, Actuator, DevTools (hands-on essentials) ✅ Dependency Injection, Component Scan & Microservices ✅ Real-world architecture questions + diagrams ✅ Advanced topics → caching, exception handling, profiles, REST versioning 💡 Whether you’re a Java backend dev, a full-stack engineer, or curious about microservice architecture, this PDF is packed with the right questions to sharpen your prep. 👉 Save this post 🔖 & keep it handy before your next interview. Follow for more Java, Spring Boot & Interview Prep resources! #SpringBoot #Java #Microservices #BackendDevelopment #FullStack #JavaInterview #SoftwareEngineer #SpringFramework #InterviewPrep #TechCareers