SumitX

All My Interview Preparation Books and Bundles in One Place Over the years, I’ve created multiple interview preparation books and digital products on Topmate and Gumroad. I regularly receive DMs asking for purchase links, so I decided to put everything in one place. If you’re preparing for technical interviews in Java, Backend, Frontend, MERN, React.js, or React Native, bookmark this post. You’ll find all the links below. Individual Books 1. Cracking the Java Interview With Sumit Topmate: topmate.io/interviewswithsum… Gumroad: msumit.gumroad.com/l/qturr Hard Copy: store.pothi.com/book/sumit-m… 2. Cracking the Backend Interviews Topmate: topmate.io/interviewswithsum… Gumroad: msumit.gumroad.com/l/fmepsw 3. Cracking the Frontend Interviews Topmate: topmate.io/interviewswithsum… Gumroad: msumit.gumroad.com/l/jfsmf 4. Cracking the MERN Interviews Topmate: topmate.io/interviewswithsum… Gumroad: msumit.gumroad.com/l/imzsr 5. Cracking the React.js Interviews Topmate: topmate.io/interviewswithsum… Gumroad: msumit.gumroad.com/l/qqheh 6. Cracking the React Native Interviews Topmate: topmate.io/interviewswithsum… Gumroad: msumit.gumroad.com/l/yakhkx Bundle Offers 1. All-in-One Bundle: Backend + Frontend + Java + React.js + MERN + React Native Topmate: topmate.io/interviewswithsum… Gumroad: msumit.gumroad.com/l/ypbkul 2. Java Interview Preparation Bundle Includes the Java Book PDF + Java Interviews in 2026 Webinar Recording. Topmate: topmate.io/interviewswithsum… 3. Java + React.js + MERN Bundle Topmate: topmate.io/interviewswithsum… Gumroad: msumit.gumroad.com/l/rikeb 4. React.js + MERN Bundle Gumroad: msumit.gumroad.com/l/rikeb 5. Java + MERN Bundle Topmate: topmate.io/interviewswithsum… Gumroad: msumit.gumroad.com/l/psdfn 6. Java + React.js Bundle Topmate: topmate.io/interviewswithsum… Gumroad: msumit.gumroad.com/l/gvabt The goal is simple: help you understand the concepts that matter, prepare for the questions interviewers ask, and approach your next opportunity with more confidence. Thank you for your continued trust and support. It genuinely means a lot.

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You need to understand - GOOD RATING MEANS NOTHING NOW !!

Was asked in JP Morgan Interview :

Interviewer: “You said your microservice is stateless. What does that mean, and why is it important?” This is a common trap question in backend interviews. Many candidates just say: “It doesn’t store session” but don’t explain why that matters. Let’s break it down: What does "stateless" actually mean? A stateless service doesn’t store any info about previous requests. Every request is treated like it's coming from scratch , no memory of "what happened before." Why is that useful? 1. Easier to scale You can add more instances without worrying about where a user's session is stored. 2. Any instance can serve any request No need to "stick" users to the same server. 3. Better fault tolerance If one server crashes, no session data is lost , another can take over instantly. Example: Imagine you're building a login system. Stateful service: Stores session data (like userId) in memory.. Stateless service: After login, you send a JWT token to the client. On every future request, the client sends this token. No session data is stored on the server. Any server can verify the token and serve the request. So a Good answer could be something like this: “Stateless means the server doesn’t store data between requests. Each request has everything needed to process it, like a token. This helps us scale easily, avoid sticky sessions.”

If you are planning to buy RO... NEVER buy @Livpure_India @LivpureSmart Livpure RO.. Their customer support is pathetic and product is also poor quality. Its been 7 days and nobody is coming..Their engineers are saying they will not come as they are not paid salaries.

Bengaluru Areas Tier List S Tier: Sarjapura

As a Java developer, Please learn: 1. Core Java Mastery - OOP principles (SOLID, DRY, KISS) - Generics, Lambda expressions, Functional interfaces - Java Streams API (map/reduce, collectors) - Java Collections framework - Java Reflection API - Exception handling 2. Multithreading & Concurrency - Thread synchronization, Executors, Locks - Fork/Join framework - Understanding of race conditions, deadlocks, and thread pools - Concurrency utilities (java.util.concurrent) 3. Design Patterns & Architecture - Common design patterns (Singleton, Factory, Builder) - Architectural patterns (MVC, - Microservices, Event-Driven Architecture) - Dependency Injection (DI), Inversion of Control (IoC) 4. Java Memory Management - Garbage Collection (G1, CMS, ZGC) - JVM heap and stack management - Profiling tools (JProfiler, VisualVM) - Analyzing memory leaks, thread dumps, and heap dumps 5. Classloaders and Reflection - Custom class loaders - Dynamic class loading - Reflection for runtime behavior manipulation 6. Spring Framework & Spring Boot - Spring Core (Dependency Injection, AOP) - Spring Boot (Auto-configuration, Microservices support) - Spring Security (OAuth2, JWT) - Spring Data (JPA, Hibernate integration) - Spring Cloud (Netflix OSS, Circuit Breakers) 7. Microservices Architecture - Service discovery (Eureka, Consul) - Load balancing, distributed tracing, and circuit breaking - API Gateway (Zuul, NGINX) - Asynchronous communication with Kafka, RabbitMQ 8. RESTful Web Services - REST principles, building APIs - JSON/XML handling - API versioning, OpenAPI/Swagger documentation 9. Java I/O and NIO - Blocking vs non-blocking I/O (NIO) - Asynchronous I/O, channels, selectors - File handling, serialization and deserialization 10. Reactive Programming - Project Reactor, RxJava - Event-driven architecture, backpressure - Reactive streams, non-blocking IO 11. JPA/Hibernate - ORM principles, entity relationships - Lazy vs eager loading - Caching strategies, query optimization 12. Database Optimization - SQL optimization, indexing, and transactions - NoSQL databases (MongoDB, Cassandra) - ACID principles, CAP theorem 13. Distributed Systems - Consistency, availability, partitioning (CAP) - Event sourcing, CQRS (Command Query Responsibility Segregation) - Distributed caching (Redis, Hazelcast) - Tools: Apache ZooKeeper, Consul, etcd 14. Testing & TDD/BDD - Unit testing (JUnit, Mockito) - Integration and functional testing - Behavior-driven development (Cucumber) 15. CI/CD & DevOps - Continuous integration (Jenkins, CircleCI) - Containerization with Docker - Orchestration with Kubernetes - Source control (Git), versioning, branching strategies 16. Performance Tuning & Optimization - JVM tuning, garbage collection optimization - Caching strategies, load balancing -Tools for profiling and monitoring (Prometheus, Grafana) 17. Security - Authentication/authorization (OAuth2, JWT) - Secure coding (OWASP guidelines) - Encryption (TLS/SSL), CSRF/XSS prevention 18. Cloud Platforms & API Gateways - AWS, Azure, GCP deployment -API Gateway (Zuul, NGINX) for rate-limiting and routing - Cloud-native microservices tools 19. Logging & Monitoring - Centralized logging (ELK Stack, Graylog) - Distributed tracing (Jaeger, Zipkin) - Application Performance Monitoring (APM) 20. Caching Mechanisms - In-memory caching (Ehcache, Caffeine) - Distributed caching (Redis, Memcached) - Cache invalidation strategies (LRU, LFU) 21. Build Tools - Maven and Gradle for dependency management - Multi-module project handling - Continuous delivery pipelines 22. Message Queuing Systems - Kafka, RabbitMQ for event-driven microservices - Pub/Sub models, distributed message brokers

With 4 cr corpus at 29 , I would say : TAKE THE OFFER !

If you are planning to buy RO... NEVER buy @Livpure_India @LivpureSmart Livpure RO.. Their customer support is pathetic and product is also poor quality.

11 Lakhs to leave Microsoft ...

User logs out, but their JWT continues to work until expiry. Is this OK ?

MICROSOFT OFFERS VOLUNTARY EXIT TO 60000 EMPLOYEES !! This is really BIG n SHOCKING!!

As a developer, have you ever wondered: How Gmail shows "Undo Send" for a few seconds? Was the email actually sent… or delayed intentionally?

As a Frontend Developer, Please slap yourself if you cannot clearly explain at least 10 of the following : Hydration Partial hydration Islands architecture Streaming SSR Concurrent rendering Time slicing Reconciliation algorithm Fiber architecture Virtual DOM diffing complexity Structural sharing Immutable data patterns Referential equality Memoization pitfalls Stale closure problem Event loop (macro vs microtasks) Task starvation Layout thrashing Critical rendering path Render blocking resources Tree shaking internals Code splitting strategies Dynamic import chunking Module federation Shadow DOM Custom Elements lifecycle Web Components interoperability Web Workers vs Service Workers SharedArrayBuffer Transferable objects OffscreenCanvas WebAssembly integration Browser compositing layers Paint vs composite vs layout GPU acceleration in CSS CSS containment Subpixel rendering IntersectionObserver internals ResizeObserver loop limits MutationObserver cost IndexedDB Service Worker lifecycle traps Cache invalidation strategies Stale-while-revalidate ETag vs Cache-Control HTTP/3 and QUIC Priority hints Preload vs Prefetch vs Preconnect CORS preflight SameSite cookie modes CSRF vs XSS mitigation Content Security Policy (CSP) DOM clobbering Prototype pollution Race conditions in UI state Tearing in concurrent UI Render waterfalls Suspense boundaries Selective hydration Server components Edge rendering Micro-frontend orchestration Finite state modeling Event sourcing in frontend Optimistic UI rollback strategy Offline conflict resolution CRDT basics for collaboration WebRTC Backpressure in streams API AbortController Streaming fetch response handling Browser memory leak detection Detached DOM nodes Garbage collection timing PerformanceObserver API Long tasks API First Input Delay (FID) Interaction to Next Paint (INP) Cumulative Layout Shift (CLS) Largest Contentful Paint (LCP) Speculative prerendering Priority inversion in async code Deterministic rendering

What is the difference between git reset and git revert?