35 High-Frequency Java & Spring Boot Interview Questions (Quick Revision Cheat Sheet)

Keshav Meena — Sat, 24 Oct 2026 12:18:02 +0000

Hey developers! 👋

While prepping for Java Backend roles, I noticed how time-consuming it is to dig through lengthy documentation, verbose blogs, or multi-hour videos right before an interview.

To streamline last-minute revision, I put together a concise 35-Question Cheat Sheet covering core Java and Spring Boot internals.

🔑 Core Topics Covered in the Cheat Sheet

1. Core Java & Collections Internals

HashMap vs ConcurrentHashMap: Bucket structure, segment locking vs CAS, rehashing mechanics, and thread-safety trade-offs.
String Pool & Immutability: Heap memory allocation, garbage collection behavior, and string literals vs new String().

2. Multithreading & Concurrency

Concurrency Primitives: volatile keyword guarantees, visibility vs atomicity.
Executors & Futures: ExecutorService thread-pool behavior, rejection policies, and CompletableFuture async pipelines.

3. Spring Boot & Microservices

Spring Core Mechanics: @EnableAutoConfiguration under the hood, @Bean vs @Component.
Error Handling & Fault Tolerance: Centralized @ControllerAdvice exception handling and Resilience4j Circuit Breaker state transitions.

4. Persistence & Database (JPA/Hibernate)

Performance Tuning: Fixing N+1 select queries, proxy initialization, and fetch strategies (LAZY vs EAGER).

📚 Get the Complete 35-Question Revision PDF Pack

If you want the full structured PDF with detailed questions and answers for quick revision:

👉 Download the Java & Spring Boot Interview Cheat Sheet (₹49)

Hope this breakdown proves helpful in your technical interview prep! Feel free to share your thoughts or drop questions in the comments below.

DEV Community: Keshav Meena

Quick revision breakdown covering core Java internals, Spring Boot mechanics, multithreading, and JPA fixes for backend developer interviews! 🚀