Hardik Chauhan

Most Imp. React interview questions with answers for 5+ yrs exp. (Par 1) 1️⃣ What is React Fiber? React Fiber is a complete rewrite of React’s reconciliation engine (how React figures out what changed in your UI). It breaks rendering work into small units (“fibers”) that can be paused, resumed, or aborted. This enables features like concurrent rendering, interruptibility, and smoother UIs. Why the rewrite? The old “stack reconciler” was synchronous → once it started rendering, it couldn’t stop. Fiber gave React a modern scheduling system. 2️⃣ Why was Fiber needed? The old reconciler had major limitations: • Rendering was blocking — could freeze the UI for large trees • Couldn’t prioritize important updates (e.g., user input) • Couldn’t pause or resume rendering • No mechanism for time slicing or concurrency Fiber solved all of this by turning rendering into small tasks React can schedule intelligently. 3️⃣ Render Phase vs Commit Phase Render Phase (Reconciliation) • Calculates what needs to change • Can be paused, aborted, or redone • Must remain pure → no side effects • Output: a list of DOM mutations to apply Commit Phase • Applies DOM changes • Runs effects (useEffect, layout effects) • Not interruptible • Must run to completion Only the commit phase can touch the DOM or perform side effects. 4️⃣ How does React decide what to re-render? React re-renders a component when: • Its state changes • Its props change • Its context value changes • A parent re-renders and the child is not memoized Then React compares the new virtual tree with the previous one to determine what actually needs to update. 5️⃣ What is “interruptible rendering”? Interruptible rendering means React can: • Start rendering work • Pause it to handle higher-priority updates • Resume later • Throw away work if newer updates arrive This is the foundation of Concurrent Mode, making React feel responsive even under heavy load. #ReactInterview #InterviewPreperation #Interview #NextJs #ReactJs

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$𝟭.𝟴𝗠 𝘀𝗽𝗲𝗻𝘁 𝗼𝗻 𝗔𝗜. 𝗭𝗲𝗿𝗼 𝗥𝗢𝗜. 𝗖𝗘𝗢 𝗵𝗮𝗱 𝗻𝗼 𝗶𝗱𝗲𝗮. EchoData Pvt. Ltd. just audited a mid-market manufacturer. 8 AI projects running. All in "pilot phase" for 12+ months. Not one in production. 𝗧𝗵𝗲 𝗯𝗿𝗲𝗮𝗸𝗱𝗼𝘄𝗻: 𝗜𝗻𝘃𝗲𝗻𝘁𝗼𝗿𝘆 𝗔𝗜: 14 months, $340K → still testing 𝗩𝗶𝘀𝗶𝗼𝗻 𝘀𝘆𝘀𝘁𝗲𝗺: 11 months, $280K → "training the model" 𝗣𝗿𝗲𝗱𝗶𝗰𝘁𝗶𝘃𝗲 𝗺𝗮𝗶𝗻𝘁𝗲𝗻𝗮𝗻𝗰𝗲: 18 months, $420K → "accuracy issues" 5 more projects, same story. How did this happen? Each department got budget. Each hired vendors. Each project looked good on slides. Nobody wanted to admit failure. 𝗧𝗵𝗲 𝗽𝗮𝘁𝘁𝗲𝗿𝗻: 𝙈𝙤𝙣𝙩𝙝 1-3: "𝙏𝙝𝙞𝙨 𝙬𝙞𝙡𝙡 𝙩𝙧𝙖𝙣𝙨𝙛𝙤𝙧𝙢 𝙪𝙨!" 𝙈𝙤𝙣𝙩𝙝 6: "𝙒𝙚 𝙣𝙚𝙚𝙙 𝙢𝙤𝙧𝙚 𝙙𝙖𝙩𝙖" 𝙈𝙤𝙣𝙩𝙝 12: "𝘼𝙄 𝙞𝙨 𝙘𝙤𝙢𝙥𝙡𝙚𝙭, 𝙩𝙖𝙠𝙚𝙨 𝙩𝙞𝙢𝙚" 𝙈𝙤𝙣𝙩𝙝 18: 𝙎𝙞𝙡𝙚𝙣𝙘𝙚 We killed 6 of 8 projects. Saved $1.2M/year. Focused on the 2 that mattered. CEO's response: "Why didn't we do this sooner?" Quick test - can you answer these right now:  • 𝗧𝗼𝘁𝗮𝗹 𝗔𝗜 𝘀𝗽𝗲𝗻𝗱 𝗮𝗰𝗿𝗼𝘀𝘀 𝘆𝗼𝘂𝗿 𝗰𝗼𝗺𝗽𝗮𝗻𝘆?  • 𝗪𝗵𝗶𝗰𝗵 𝗽𝗿𝗼𝗷𝗲𝗰𝘁𝘀 𝗱𝗲𝗹𝗶𝘃𝗲𝗿𝗲𝗱 𝗥𝗢𝗜 𝗹𝗮𝘀𝘁 𝗾𝘂𝗮𝗿𝘁𝗲𝗿?  • 𝗪𝗵𝗶𝗰𝗵 𝗽𝗶𝗹𝗼𝘁𝘀 𝗵𝗮𝘃𝗲 𝗿𝘂𝗻 𝟭𝟮+ 𝗺𝗼𝗻𝘁𝗵𝘀? If you hesitated, you have the problem. Let's Connect! #AIStrategy #DigitalTransformation

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People from non-tech backgrounds are making 20-30 lacs as QAs at FAANG. People from BPOs have become successful QAs teams rely on. Even people who’ve never written a single line of code have become good QAs. I’m not saying this to motivate you. I’m saying it because I’ve done it. I started my career at a non-tech KPO with a role that most engineers would never apply for. It required no tech or automation. But every day, I kept asking myself “What can I improve?” “What can I fix before someone else finds it?” That mindset helped me stand out, even in a non-tech job. Later, I joined Amazon, but still in a non-technical role. Same story repeated : → Spent weekends learning Selenium and writing test cases → Asked engineers to walk me through bugs → Looked at every process and thought, “How do I make this better?” Eventually, I moved into a full-time QA role with the help of manager who noticed and appreciated my work. Today, I’m a QA II at Amazon. Here’s what I’ve learned: - You don’t need a CS degree to start. - You don’t need perfect answers. - You just need curiosity, consistency, and the guts to raise your hand and ask, "Can I take a shot at this?" That one habit changed everything for me. And it might just change things for you, too. P.S. I'm Raghvendra, a QA II at Amazon. I share real stories and practical lessons from my journey in QA, automation, and career growth. Follow along if that’s the path you’re on, too.

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🔥 Pointers in C: Fear Factor নাকি Real Power? C শেখার সময় সবচেয়ে scary জিনিস? 👉 Pointers 😅 কিন্তু truth হলো— Pointers = C-এর backbone 💀 কেন এত important? • 🧠 Dynamic memory → malloc/free দিয়ে runtime control • 🔁 Pass by reference → original variable change • 📦 Array, string, linked list-এর base • ⚙️ Embedded / OS / low-level → hardware direct access • ⚡ Performance → extra copy ছাড়াই fast কাজ 🔑 Analogy: Pointer = ঘরের চাবি ভুল ব্যবহার করলে 👉 segmentation fault 😂 👉 Pointers skip করলে C half-done। #CProgramming #Pointers #CodingLife #LearnC #TechCommunity

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## How to Use Zero Downtime Deployments: Blue-Green and Canary Quickly? Caching at the right layer can reduce database load by orders of magnitude. Here is a quick example to get started: ```js // Rate limiter using Token Bucket (conceptual) class TokenBucket { constructor(capacity, refillRatePerSec) { this.capacity = capacity; this.tokens = capacity; this.refillRate = refillRatePerSec; setInterval(() => { this.tokens = Math.min(this.capacity, this.tokens + this.refillRate); }, 1000); } consume() { if (this.tokens > 0) { this.tokens--; return true; } return false; } } ``` ## What is Zero Downtime Deployments: Blue-Green and Canary? Caching at the right layer can reduce database load by orders of magnitude. Understanding this concept is essential for writing reliable, maintainable code. It forms the foundation for many advanced patterns you will encounter in production applications. When applied correctly, it improves code readability and reduces bugs during development and maintenance cycles. ## When to Use Zero Downtime Deployments: Blue-Green and Canary? You should use this approach when: - Building features that depend on prefer simple proven comp

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❓️Why was finalize() removed (or deprecated) in newer Java versions? 📌 Reasons in short • finalize() is deprecated (Java 9) and essentially removed (Java 18+). • It was slow, unsafe, and unreliable. • we can use AutoCloseable, try-with-resources, or Cleaner instead. • Modern Java promotes explicit and predictable resource management.

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Spring Batch for Uploading CST Salary File (with Code Snippets) Implemented a Spring Batch flow to process the monthly CST salary file. It runs 28th every month at 1 AM, validates records, calls payment REST API, and stores request/response JSON in an audit table. ⸻ ✅ 1. Job Scheduler (28th @ 1 AM CST) @Scheduled(cron = "0 0 1 28 * ?") public void runCstFileJob() { jobLauncher.run(cstJob, new JobParameters()); } ⸻ ✅ 2. File Reader (CSV / Excel) @Bean public FlatFileItemReader<SalaryRecord> reader() { return new FlatFileItemReaderBuilder<SalaryRecord>() .name("salaryReader") .resource(new FileSystemResource("/opt/files/cst-file.csv")) .delimited() .names("empId","accNo","amount") .targetType(SalaryRecord.class) .build(); } ⸻ ✅ 3. Processor (Validation + Prepare API Request) @Bean public ItemProcessor<SalaryRecord, PaymentRequest> processor() { return record -> { if (record.getAmount() <= 0) return null; return new PaymentRequest(record.getEmpId(), record.getAccNo(), record.getAmount()); }; } ⸻ ✅ 4. Writer (REST Call + Audit Logging) @Bean public ItemWriter<PaymentRequest> writer() { return items -> { for (PaymentRequest req : items) { String reqJson = new ObjectMapper().writeValueAsString(req); ResponseEntity<String> resp = restTemplate.postForEntity("https://payment/api/pay", req, String.class); String respJson = resp.getBody(); auditRepo.save(new AuditLog(reqJson, respJson, LocalDateTime.now())); } }; } ⸻ ✅ 5. Batch Job Config @Bean public Job cstJob(JobRepository repo, Step cstStep) { return new JobBuilder("cstSalaryJob", repo) .start(cstStep) .build(); } @Bean public Step cstStep(JobRepository repo, PlatformTransactionManager tx) { return new StepBuilder("cstStep", repo) .<SalaryRecord, PaymentRequest>chunk(100, tx) .reader(reader()) .processor(processor()) .writer(writer()) .build(); } ⸻ ✔️ What This Delivers • Automated bulk salary processing • High-performance chunk-based parallel execution • REST-driven payment processing • Full audit trail with JSON request/response • Reliable monthly job at 1 AM CST ⸻

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🚀 Spring Boot Tip: @Value vs @ConfigurationProperties In Spring Boot, both @Value and @ConfigurationProperties help us inject values from application.properties / application.yml. But when should we use which? 🤔 Let’s break it down 👇 ✅ Using @Value Best for injecting single or simple properties. application.properties app.title=Online Banking System app.maxUsers=500 Java Example @Component public class AppConfig { @Value("${app.title}") private String title; @Value("${app.maxUsers}") private int maxUsers; public void printConfig() { System.out.println("Title: " + title); System.out.println("Max Users: " + maxUsers); } } 👉 Use this when you just need 1–2 direct values. ✅ Using @ConfigurationProperties Best for grouping related properties into a structured class. application.yml bank: name: XYZ Bank branch: Pune limits: minBalance: 1000 maxTransfer: 50000 Java Example @Configuration @ConfigurationProperties(prefix = "bank") public class BankConfig { private String name; private String branch; private Limits limits; // getters & setters public static class Limits { private int minBalance; private int maxTransfer; // getters & setters } } 👉 Use this when you have multiple related configurations. It keeps code clean, readable, and scalable. . ✨ Key takeaway: Use @Value → quick, single values. Use @ConfigurationProperties → structured configs, cleaner code, supports type-safety & validation. ✅ Real-time Example (Banking): @Value → Injecting a single property like bank.ifscCode. @ConfigurationProperties → Mapping multiple properties like bank.name, bank.branch, bank.contact into a BankProperties class. 👉 Which one do you prefer in your projects? #SpringBoot #Java #Microservices #SpringFramework #CodingTips

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When to Use BFF (Backend for Frontend) Backend for Frontend (BFF) is used when different client applications need customized backend APIs instead of a one-size-fits-all backend. Use BFF in the following situations: 1. Multiple Frontends with Different Needs • Web, mobile, and tablet apps require different data formats or workflows. • Example: Mobile needs lightweight responses, web needs detailed data. 2. Avoid Over-Fetching or Under-Fetching • A common backend returns too much or too little data. • BFF tailors responses exactly for the frontend. 3. Complex UI Aggregation • Frontend needs data from multiple microservices. • BFF aggregates responses and reduces frontend logic. 4. Independent Frontend Development • Frontend teams can evolve APIs without impacting others. • Faster UI changes without touching core services. 5. Security and Access Control • BFF hides internal microservices from direct access. • Enforces frontend-specific authentication and authorization. 6. Different Performance Requirements • Mobile apps require fewer calls and optimized payloads. • BFF improves performance by reducing network calls. 7. API Versioning Simplification • BFF manages API versions per frontend. • Core services remain stable. When NOT to Use BFF • Single frontend with simple API needs. • Small applications where added complexity is unnecessary. • When GraphQL already solves data-fetching problems effectively. 👉 In short: Use BFF when you have multiple frontends with different requirements and want clean separation, performance optimization, and faster UI evolution 😊

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Why Amazon S3 Is NOT a Full Version Control System 🗂️ What is Amazon S3? ==================== Amazon Web Services S3 (Simple Storage Service) is an object storage service. It is mainly used to store files like: Images Logs Backups Application data Static website files It is not designed to manage code collaboration like a true Version Control System (VCS). 🔎 What is a Version Control System? ================================ A Version Control System (VCS) like Git or platforms like GitHub: Tracks code changes line-by-line Allows multiple developers to collaborate Supports branching & merging Maintains commit history with messages Helps resolve conflicts It is specially built for software development. Why S3 is NOT Considered a True Version Control System Even though S3 has Versioning Feature, it is still not a real VCS. Here’s why: 1️⃣ No Line-by-Line Tracking S3 stores full file versions. It does not track what exactly changed inside the file. In Git: You can see which line was added or deleted. In S3: You only see “File Version 1, Version 2, Version 3.” 2️⃣ No Branching or Merging Git supports: Branch creation Merge requests Conflict resolution S3: No branching No merge logic No collaboration workflow 3️⃣ No Developer Collaboration Features S3 does not provide: Commit history with messages Pull requests Code reviews Conflict handling It just stores object versions.

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Company: Capgemini Location: Pan India Role: Consultancy level B2 Rounds: 2 Technical + 1 Managerial Offer Received: ✔️ Round 1 – Technical (Core Java Basics) 1. Difference between JDK, JRE, and JVM. 2. Difference between ArrayList and LinkedList. 3. Difference between HashMap and HashSet. 4. What is method overloading vs method overriding? 5. What is encapsulation, inheritance, and polymorphism in Java? 6. What is the difference between interface and abstract class? 7. What is exception handling in Java and difference between checked and unchecked exceptions? 8. What is Optional in Java 8 and why is it useful? 9. Difference between map() and filter() in Java Streams. 10. What are REST APIs and common HTTP methods? Scenario 11. If your API response becomes slow, what steps will you take to debug it? 12. How would you optimize a slow database query? Round 2 – Technical (Multithreading & Concurrency – Deep Dive) 1. Difference between process and thread. 2. Difference between Runnable and Callable. 3. What is synchronization and why is it required? 4. Difference between synchronized block and ReentrantLock. 5. What is deadlock, and how can it be prevented? Advanced Multithreading 6. Explain Java Memory Model (JMM) with an example. 7. Difference between volatile and Atomic variables. 8. How does ConcurrentHashMap achieve thread safety? 9. Explain ForkJoinPool and work-stealing algorithm. 10. What is CompletableFuture, and how does it help in asynchronous programming? Scenario-Based 11. Suppose 1000 threads are updating the same counter, how will you design it safely? 12. Your thread pool is getting exhausted in production, how will you troubleshoot it? 13. Your application suddenly shows thread deadlocks, how will you identify and fix them? 14. If multiple services access the same shared resource, how would you ensure consistency? Round 3 – Managerial 1. Tell me about a challenging issue you solved in a project. 2. How do you handle tight deadlines in projects? 3. How do you ensure code quality in your team? 4. How do you handle conflicts within a development team? 5. How do you mentor junior developers? Hope this helps developers preparing for Java Backend interviews.please follow Neelesh Mohanty I will keep sharing more interview questions from other companies as well. Follow me for such content on Java, Backend, and Interview Preparation. #JavaDeveloper #JavaInterview #DSAPreparation #CodingInterviewPrep #BackendDevelopment #SoftwareEngineering #TechCareers #Java #Interview #InterviewPreparation #DSA #Jobchange

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* Scenario 6: Auto-Generate Short Description (Client Script)  * Description: Generate short description based on caller and category.  */ function onLoad() {    var caller = g_form.getDisplayValue('caller_id');    var category = g_form.getValue('category');    if (caller && category) {        g_form.setValue('short_description', caller + ' - ' + category + ' Issue');    } } #ServiceNow #ServiceNowDeveloper #CMDB #ITSM #ITOperations #ConfigurationManagement #DigitalTransformation #Automation #NowPlatform #TechCommunity #CloudComputing #EnterpriseIT #DevOps #ServiceNowCommunity #WorkflowAutomation

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🚀 Angular Insight: Smart vs Dumb Components (Real Architecture Game Changer) Zyada tar Angular apps me sab logic component me daal diya jata hai 😅 ❌ API call bhi wahi ❌ Business logic bhi wahi ❌ UI logic bhi wahi Result? Spaghetti components 🍝 ✅ Senior Approach: Smart & Dumb Component Pattern 🧠 Smart Component (Container) API call karega State manage karega Data pass karega @Component({...}) export class UserContainerComponent { users$ = this.userService.getUsers(); } 🎯 Dumb Component (Presentational) Sirf @Input lega UI render karega @Output emit karega @Component({...}) export class UserListComponent { @Input() users!: User[]; @Output() select = new EventEmitter<User>(); } 🔥 Why This Is Powerful? ✔ Reusable UI components ✔ Easy unit testing ✔ Clear separation of concerns ✔ Scalable enterprise architecture ✔ Clean folder structure 💡 Real Senior Mindset: “Business logic belongs to containers, not UI components.” #Angular #FrontendArchitecture #CleanCode #SeniorDeveloper #AngularTips

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🚀 Cracking Any Tech Interview (FAANG + Big Giant Tech Companies) Topic: Matrix – Rotate Image (In-Place) Q. You are given an n x n 2D matrix representing an image. Rotate the image by 90 degrees (clockwise). You must do it in place. (Frequently asked at Google, Facebook, Amazon) Example Input: [[1,2,3], [4,5,6], [7,8,9]] Output: [[7,4,1], [8,5,2], [9,6,3]] 🔹 Approach 1: Transpose + Reverse Rows 1. Transpose matrix (swap across diagonal). 2. Reverse each row. Time: O(n²), Space: O(1). 🔹 Approach 2: Layer-by-Layer Rotation Rotate elements in groups of 4 for each layer. Time: O(n²), Space: O(1). ✅ Code (Python) def rotate(matrix): n = len(matrix) # Transpose for i in range(n): for j in range(i, n): matrix[i][j], matrix[j][i] = matrix[j][i], matrix[i][j] # Reverse rows for row in matrix: row.reverse() ✅ Code (C#) public void Rotate(int[][] matrix) { int n = matrix.Length; // Transpose for (int i = 0; i < n; i++) { for (int j = i; j < n; j++) { int temp = matrix[i][j]; matrix[i][j] = matrix[j][i]; matrix[j][i] = temp; } } // Reverse each row for (int i = 0; i < n; i++) { Array.Reverse(matrix[i]); } } 📌 Follow-up Question How would you rotate the matrix 180° or 270° in place? 🔑 Takeaway: Matrix rotation tests your ability to manipulate 2D arrays and apply systematic transformations. #CrackFAANG #BigTechPrep #CodingInterview #DSA #LeetCode #Matrix #InterviewPreparation

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🚀 Java Application Performance – It’s More Than Just Code! The performance of any Java-based application is influenced by multiple factors working together: 🔹 JVM tuning (heap size, GC, parameters) 🔹 JIT compiler optimizations 🔹 Thread pool configuration 🔹 Application server tuning And that’s just the beginning… 💡 Writing efficient code also matters: - Proper use of String pool - Understanding Java references - Effective locking mechanisms - Leveraging lambdas wisely 🏗️ Architecture plays a critical role: - JDBC vs ORM decisions - Synchronous vs asynchronous processing - Distributed system design - Cloud-native patterns 👉 Performance is not a single change — it’s a mindset and a combination of best practices across layers. If you want to gain deep, practical insights into Java performance tuning and best practices, I’m conducting a focused workshop. 📩 Interested? Reach out at: jbossramana@gmail.com Let’s build high-performance, scalable Java applications together. #Java #PerformanceTuning #Microservices #JVM #CloudNative #SoftwareArchitecture

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🚦 JavaScript isn’t “slow”… your understanding of it might be! 😎 Ever wondered how JS handles timeouts, promises, fetch calls, and still stays smooth on a single thread? Meet the Event Loop — the real MVP working behind the scenes. 🔄⚡ 💡 Call Stack → Web APIs → Queues → Event Loop It’s like a nightclub bouncer deciding who enters next. 😂 Event Loop makes asynchronous JavaScript possible by continuously checking the call stack and scheduling tasks from microtask and callback queues. 👨‍💻 Master this, and async code will never confuse you again. #javascript #frontend #nodejs

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🚀 PHP Advance & OOPs Interview Questions With Answer 👨‍💻 Agar aap PHP Developer interview ke liye prepare kar rahe ho, to ye questions zaroor yaad rakho 👇 1️. What is the difference between == and === in PHP? Answer: == sirf value compare karta hai, type convert karke. === value + data type dono compare karta hai. Isliye strict comparison ke liye always === use hota hai. 2️. What is the meaning of “call by value” and “call by reference”?  Answer:   Call by value: Function ko variable ki copy milti hai. Original value change nahi hoti.  Call by reference: Function ko variable ka actual reference milta hai, matlab original value change ho sakti hai. 3️. What is OOP in PHP?  Answer:  OOP ka matlab hai Object Oriented Programming, jisme hum code ko classes aur objects me divide karte hain.  Key concepts: Encapsulation, Inheritance, Polymorphism, Abstraction. 4️. What is the use of namespace in PHP?  Answer:  Namespace conflicts avoid karta hai.  Agar 2 classes ka naam same ho, namespace use karke hum unhe uniquely identify kar sakte hain. 5️. What is Traits in PHP?  Answer:  Trait ek reusable code block hota hai jo class me include kiya ja sakta hai.  Useful jab PHP me multiple inheritance directly possible nahi hota. 6️. What is the difference between include, require, include_once, require_once?  Answer:  - include: File missing ho to warning, script continue.  - require: File missing ho to fatal error, script stop.  - include_once / require_once: File sirf ek baar load hogi (duplicate include roke). 7️. What is PDO in PHP?  Answer:  PDO (PHP Data Object) database access ka secure & flexible tarika.  Yeh prepared statements support karta hai -> SQL injection se protection. 8️. What are Prepared Statements?  Answer:  Prepared statements SQL ko pre-compile kar dete hain, jisse:  Security better (SQL Injection safe)  Performance fast hota hai 9️. What is Composer in PHP?  Answer:  Composer PHP ka dependency management tool hai.  Aap kisi bhi library / package ko easily install & manage kar sakte ho (e.g. Laravel packages). 1️0. What is the use of CSRF token in Laravel?  Answer:  CSRF token request ko verify karta hai ki woh trusted source se aa rahi hai.  Yeh Cross-Site Request Forgery attack se protect karta hai. #PHP #OOP #WebDevelopment #Laravel #Backend #InterviewPreparation #Coding #DevelopersCommunity

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ARTICTURE CHANGES IN SOFTWARE ENGINEER:- i think In upcoming Articture of Software engineering, there will be design of Agent, which I means is that, there will respective agents for each services, For eg if it is payments there will be a separate agents for the Payments which will handle all the payments of the company, if it's a notification service, so it will handle all the notification service based on the context it's get not on the api call for that , and on Orchestration there will be agents to agents communication, working on the behalf of you. VALUE CREATION IJ FUTURE:- i think it's the decision you take and context you provide to these agents extraction of work from the agents will be very valuable,

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