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Java Full Stack with React Interview Questions in Chennai

36 practice questions with answers for Java Full Stack with React interviews in Chennai.

Java Full Stack with React jobs in Chennai

Chennai is a long-standing IT-services and SaaS hub along OMR, with strong demand for testing, data and support-engineering roles. Many companies here hire freshers in large batches and train them on the job.

Below are 36 questions that match the mix of service, product and domain employers hiring java full stack developers in Chennai.

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01

What is a closure in JavaScript? Give a practical use.

JavaScript, HTML and CSSMedium
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A closure is a function that remembers variables from the scope where it was created, even after that outer function has returned. For example, function counter() { let n = 0; return () => ++n; } returns a function that keeps its own private n. Closures are used for data privacy, function factories, event handlers, debounce and memoization, and React hooks rely on them. Stale closures in effects are a common bug when dependencies are missing.
02

The layout looks fine on desktop but breaks on mobile with horizontal scrolling. How do you debug it?

JavaScript, HTML and CSSEasy
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Check that the page has the viewport meta tag. Use browser device mode to find the element wider than the screen, often fixed widths in pixels, large images, long words or tables. Replace fixed widths with max-width: 100 percent, flexible units and flex-wrap, add overflow-wrap for long text and wrap wide tables in a scrollable container. Build mobile-first with media queries that add complexity for larger screens.
03

What are cascade types and orphanRemoval in JPA?

JPA and HibernateMedium
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Cascade propagates operations from a parent to its children: PERSIST, MERGE, REMOVE, REFRESH, DETACH or ALL. For example, saving an Order with CascadeType.ALL also saves its items. orphanRemoval = true deletes a child row when it is removed from the parent's collection. Use them for true parent-child aggregates like order and items, but never cascade REMOVE on @ManyToOne or shared references like Category, or deleting one product could delete the category.
04

Explain Inversion of Control and Dependency Injection.

Spring BootEasy
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Inversion of Control means the framework, not your code, creates and wires objects. Dependency Injection is how Spring does it: a class declares what it needs, usually through its constructor, and the container supplies the beans. For example, OrderService receives an OrderRepository instead of creating one with new. This reduces coupling, makes it easy to swap implementations and lets you pass mocks in unit tests.
05

Find the top 3 highest-paid employees in each department.

SQL and DatabasesMedium
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SELECT department_id, name, salary FROM ( SELECT department_id, name, salary, DENSE_RANK() OVER ( PARTITION BY department_id ORDER BY salary DESC) AS rnk FROM employees ) ranked WHERE rnk <= 3 ORDER BY department_id, rnk; -- DENSE_RANK keeps ties; use ROW_NUMBER for exactly 3 rows.
06

You are loading about five lakh records into an ArrayList and a HashMap and memory spikes during loading. What can you do?

Collections and StreamsMedium
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Both collections resize by copying when they grow, which causes temporary memory spikes. Pre-size them, for example new ArrayList<>(500000) and HashMap with capacity of expected size divided by 0.75. Better still, avoid holding everything at once: process the data in batches or stream it from the database with pagination. Use primitive-friendly structures or IntStream where possible to avoid boxing overhead.
07

Find employees who earn more than their managers.

SQL and DatabasesMedium
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SELECT e.name AS employee, e.salary, m.name AS manager, m.salary AS manager_salary FROM employees e JOIN employees m ON e.manager_id = m.id WHERE e.salary > m.salary; -- A self join treats the same table as two roles.
08

Find duplicate elements in a list of integers.

Collections and StreamsEasy
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List<Integer> nums = List.of(4, 2, 7, 2, 4, 9); Set<Integer> seen = new HashSet<>(); Set<Integer> duplicates = nums.stream() .filter(n -> !seen.add(n)) .collect(Collectors.toSet()); System.out.println(duplicates); // [2, 4] // Stateless alternative using counts: // nums.stream().collect(groupingBy(identity(), counting())) // .entrySet().stream().filter(e -> e.getValue() > 1)
09

Compare promises and async/await.

JavaScript, HTML and CSSMedium
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A promise represents a value that will be available later, handled with then, catch and finally. async/await is syntax built on promises: an async function always returns a promise, and await pauses that function until the promise settles, so asynchronous code reads like synchronous code. Errors are handled with try/catch. Awaiting calls one by one is sequential, so use Promise.all for independent calls to run them in parallel.
10

How do code splitting and lazy loading work in React?

React FrontendMedium
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Code splitting breaks the JavaScript bundle into smaller chunks loaded on demand, which improves first load time. React.lazy with a dynamic import, such as const Reports = lazy(() => import('./Reports')), loads the component only when it renders, and Suspense shows a fallback while it loads. Splitting by route is the most common pattern. Bundlers like Vite create the chunks automatically from dynamic imports.
11

Write a query to find the second highest salary from an employees table.

SQL and DatabasesEasy
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-- Using a subquery SELECT MAX(salary) AS second_highest FROM employees WHERE salary < (SELECT MAX(salary) FROM employees); -- Using DISTINCT with OFFSET SELECT DISTINCT salary FROM employees ORDER BY salary DESC LIMIT 1 OFFSET 1; -- The first query returns NULL when there is no second salary.
12

Write code that runs tasks in parallel using ExecutorService and collects results.

Core JavaMedium
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ExecutorService pool = Executors.newFixedThreadPool(4); try { List<Callable<Integer>> tasks = List.of( () -> fetchCount("orders"), () -> fetchCount("users")); List<Future<Integer>> results = pool.invokeAll(tasks); for (Future<Integer> f : results) { System.out.println(f.get()); } } finally { pool.shutdown(); } // On Java 21 you can use Executors.newVirtualThreadPerTaskExecutor() // for I/O-bound tasks.
13

What is Spring Boot Actuator used for?

Spring BootMedium
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Actuator adds production-ready endpoints for monitoring and management, such as /actuator/health, /actuator/info, /actuator/metrics and /actuator/prometheus. Kubernetes uses health liveness and readiness groups for probes. Metrics are collected through Micrometer and can be exported to Prometheus, Datadog or other systems. Only expose the endpoints you need with management.endpoints.web.exposure.include and secure them, because endpoints like env or heapdump can leak sensitive data.
14

How do you learn a new framework or library quickly when a project needs it?

JPA and HibernateEasy
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I start with the official getting-started guide and build a tiny working example, then read how it is used in our codebase. For example, when our team adopted Flyway, I created a sample project, tried failure cases like a bad migration and wrote a one-page guide for the team. Within a week I was handling migrations in the main project. I also note questions and clarify them with seniors early instead of guessing.
15

How do you keep yourself updated with new Java versions and features?

Collections and StreamsEasy
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I follow the six-monthly Java release notes and JEP summaries, and I try new features in small jshell experiments or side projects. For example, when Java 21 became LTS I rewrote a small file-processing tool using virtual threads and pattern matching to understand the benefits. I also read Spring release blogs and watch conference talks, and I share short notes with my team so we upgrade with confidence.
16

What is normalization? Explain 1NF, 2NF and 3NF.

SQL and DatabasesMedium
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Normalization organises tables to reduce redundancy and update anomalies. 1NF requires atomic values with no repeating groups. 2NF requires 1NF and that every non-key column depends on the whole primary key, not part of a composite key. 3NF requires 2NF and no transitive dependency, so non-key columns depend only on the key. For example, store customer city in the customers table, not in every order row. Reporting systems sometimes denormalize for speed.
17

Why should we hire you as a Java full stack developer?

JavaScript, HTML and CSSMedium
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I can contribute on both sides of a feature: I have built REST APIs with Spring Boot, JPA and MySQL, and responsive React screens that consume them. I write tests, use Git properly and have deployed my projects with Docker. I also learn quickly; I picked up Spring Security and JWT for my capstone in two weeks. I am looking for a team where I can grow into an engineer who owns features from design to production.
18

Your component keeps re-rendering in an infinite loop after calling an API. What is wrong?

React FrontendMedium
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Usually useEffect sets state and has a dependency that changes on every render, or has no dependency array at all. A common case is an object or function created inside the component and listed as a dependency, so it is new each time. Fix it by using a correct dependency array, moving the object outside the component, or memoizing it with useMemo or useCallback. Also check that you are not calling setState directly during render.
19

After calling setCount(count + 1), console.log(count) still shows the old value. Why?

React FrontendMedium
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State updates are scheduled, not applied immediately. The count variable in the current render is a constant snapshot, so logging right after setState shows the old value; the new value appears in the next render. React also batches multiple updates. When the next state depends on the previous one, use the updater form setCount(c => c + 1), which works correctly even when called several times. Use useEffect to react to the updated value.
20

When should you use useMemo and useCallback?

React FrontendMedium
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useMemo caches the result of an expensive calculation until its dependencies change, such as filtering and sorting a big list. useCallback caches a function reference, which matters when passing callbacks to children wrapped in React.memo or used in effect dependencies. Do not wrap everything, because memoization itself has a cost. The React Compiler, released as stable in 2025, can add much of this memoization automatically in supported projects.
21

Write a repository query that loads orders with their items in one query.

JPA and HibernateMedium
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public interface OrderRepository extends JpaRepository<Order, Long> { @Query(""" select distinct o from Order o join fetch o.items i where o.customer.id = :customerId """) List<Order> findWithItems(@Param("customerId") Long customerId); @EntityGraph(attributePaths = {"items", "customer"}) Optional<Order> findWithGraphById(Long id); }
22

What is the N+1 select problem and how do you solve it?

JPA and HibernateMedium
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It happens when one query loads N parent rows and then each lazy association fires a separate query, giving N+1 queries. For example, listing 100 orders and calling getCustomer on each. Solve it with JOIN FETCH in JPQL, @EntityGraph on the repository method, batch fetching with hibernate.default_batch_fetch_size, or DTO projections that select only the needed columns. Enable SQL logging or a statistics tool in development to catch it early.
23

Database passwords and API keys are committed in application.properties. How do you fix this?

Spring BootMedium
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Remove the secrets from the repository, rotate the exposed credentials immediately, and clean the history if needed. Replace values with placeholders such as ${DB_PASSWORD} and supply them through environment variables, Kubernetes Secrets or a vault like HashiCorp Vault or a cloud secrets manager. Add a pre-commit secret scanner, keep local values in an ignored file, and give each environment its own credentials with least privilege.
24

Returning an entity from a REST API causes infinite recursion in JSON. Why, and how do you fix it?

JPA and HibernateMedium
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Bidirectional relationships, such as Order having items and each item referencing its order, make Jackson serialise back and forth endlessly, leading to StackOverflowError. The cleanest fix is to return DTOs instead of entities, so you control exactly what is exposed. Quick fixes include @JsonManagedReference with @JsonBackReference or @JsonIgnore on one side. DTOs also stop lazy loading during serialisation and avoid leaking internal fields.
25

How does garbage collection work in modern Java?

Core JavaMedium
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The GC frees objects that are no longer reachable from GC roots such as thread stacks and static fields. Most objects die young, so the heap is generational: minor collections clean the young generation often and survivors are promoted. G1 is the default collector since Java 9 and targets predictable pause times by collecting regions. ZGC and Shenandoah offer sub-millisecond pauses for large heaps. Tuning usually starts with -Xmx and choosing the collector, not dozens of flags.
26

How do you work with frontend developers and testers on API changes?

REST APIs, Security and MicroservicesEasy
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I agree on the API contract first using an OpenAPI spec or Swagger UI, so frontend and QA can start in parallel with mock data. I share example requests and error responses, and I tell the team early if a field must change. For example, in my last sprint I gave QA a Postman collection with test cases for every endpoint. This reduced back-and-forth and our feature passed testing on the first cycle.
27

How does the this keyword work, and how do arrow functions change it?

JavaScript, HTML and CSSMedium
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In a regular function, this depends on how the function is called: the object before the dot in a method call, undefined in strict mode for a plain call, the new object with new, or a value set by call, apply or bind. Arrow functions do not have their own this; they use this from the surrounding scope. That makes arrows ideal for callbacks inside methods, but unsuitable as object methods that need their own this.
28

Compare monolithic and microservices architecture.

REST APIs, Security and MicroservicesMedium
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A monolith is one deployable application. It is simpler to build, test and debug, and suits small teams and early products. Microservices split the system into independently deployable services owned by separate teams, such as orders, payments and inventory, each with its own database. They allow independent scaling and releases but add network latency, distributed data, monitoring and deployment complexity. Many teams start with a modular monolith and split only when needed.
29

How do you deep clone an object in JavaScript?

JavaScript, HTML and CSSMedium
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const original = { user: { name: 'Asha' }, tags: ['a'], joined: new Date() }; // Modern built-in (handles Date, Map, Set, cycles): const copy = structuredClone(original); // Spread is only a shallow copy: const shallow = { ...original }; shallow.user.name = 'Ravi'; // also changes original.user.name // JSON.parse(JSON.stringify(obj)) loses Dates, functions, // undefined and fails on circular references.
30

A search query that used to take milliseconds now takes 10 seconds as data grew. How do you troubleshoot?

SQL and DatabasesMedium
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Get the exact SQL from logs or the slow query log and run EXPLAIN ANALYZE to see whether it does a full scan, a bad join order or a big sort. Check for missing or unused indexes, functions on indexed columns, implicit type conversions and outdated statistics. Add the right composite index, rewrite the query, select fewer columns and paginate. For text search, use a full-text index or a search engine instead of LIKE '%term%'.
31

What are fail-fast and fail-safe iterators?

Collections and StreamsMedium
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Fail-fast iterators, used by ArrayList and HashMap, track a modification count and throw ConcurrentModificationException if the collection is structurally changed during iteration, except through the iterator's own remove. Fail-safe or weakly consistent iterators, used by CopyOnWriteArrayList and ConcurrentHashMap, work on a snapshot or tolerate concurrent changes and never throw that exception, but they may not show the latest updates.
32

Your team is starting a new React project. Would you use Create React App or something else?

JavaScript, HTML and CSSMedium
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Create React App is deprecated and no longer recommended. For a single-page app backed by a Spring Boot API, Vite is the usual choice because of its fast dev server and optimised builds. If you need server-side rendering, SEO or file-based routing, a framework like Next.js or React Router in framework mode is recommended by the React team. Choose based on SEO needs, hosting and the team's experience.
33

Write a controller slice test with @WebMvcTest and MockMvc.

Spring BootHard
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@WebMvcTest(ProductController.class) class ProductControllerTest { @Autowired MockMvc mvc; @MockitoBean ProductService service; // @MockBean before Boot 3.4 @Test void returnsProduct() throws Exception { when(service.getProduct(1L)).thenReturn(new ProductDto(1L, "Pen", 20.0)); mvc.perform(get("/api/products/1")) .andExpect(status().isOk()) .andExpect(jsonPath("$.name").value("Pen")); } }
34

Sort a list of products by category, then by price descending, then by name.

Collections and StreamsMedium
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products.sort( Comparator.comparing(Product::getCategory) .thenComparing(Product::getPrice, Comparator.reverseOrder()) .thenComparing(Product::getName)); // Null-safe variant for an optional field: Comparator<Product> byBrand = Comparator.comparing( Product::getBrand, Comparator.nullsLast(Comparator.naturalOrder()));
35

When would you use the Context API and when a state library like Redux Toolkit or Zustand?

React FrontendMedium
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Context is good for passing low-frequency global values such as theme, language or the logged-in user without prop drilling. Every consumer re-renders when the context value changes, so it is not ideal for fast-changing data. Redux Toolkit or Zustand suit larger shared client state with many updates, selectors and dev tools. Server data like API responses is often best handled by TanStack Query, which adds caching and refetching.
36

How does JWT-based authentication work?

REST APIs, Security and MicroservicesMedium
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After a successful login, the server issues a JSON Web Token containing a header, a payload of claims such as user ID, roles and expiry, and a signature made with a secret or private key. The client sends it in the Authorization: Bearer header with each request. The server verifies the signature and expiry without a session lookup, which suits stateless APIs. Keep access tokens short-lived, do not store sensitive data in the payload because it is only encoded, and use refresh tokens for renewal.

Companies with offices in Chennai (11)

IT services

TCS

Java Full Stack with React interview questions

  • 30 questions
  • 4 rounds

Mumbai, Chennai, Pune +2

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IT services

Infosys

Java Full Stack with React interview questions

  • 30 questions
  • 4 rounds

Bengaluru, Mysuru, Pune +2

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IT services

Wipro

Java Full Stack with React interview questions

  • 30 questions
  • 4 rounds

Bengaluru, Hyderabad, Pune +2

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IT services

Cognizant

Java Full Stack with React interview questions

  • 30 questions
  • 4 rounds

Chennai, Bengaluru, Pune +2

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IT services

Capgemini

Java Full Stack with React interview questions

  • 30 questions
  • 4 rounds

Mumbai, Bengaluru, Pune +2

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IT services

HCLTech

Java Full Stack with React interview questions

  • 30 questions
  • 4 rounds

Noida, Chennai, Bengaluru +2

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IT services

Tech Mahindra

Java Full Stack with React interview questions

  • 30 questions
  • 4 rounds

Pune, Hyderabad, Bengaluru +2

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IT services

LTIMindtree

Java Full Stack with React interview questions

  • 30 questions
  • 4 rounds

Mumbai, Pune, Bengaluru +2

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Banking & finance

Barclays

Java Full Stack with React interview questions

  • 30 questions
  • 4 rounds

Pune, Chennai, Noida +1

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E-commerce & consumer tech

Walmart

Java Full Stack with React interview questions

  • 30 questions
  • 5 rounds

Bengaluru, Chennai, Gurugram

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IT services

EPAM Systems

Java Full Stack with React interview questions

  • 30 questions
  • 4 rounds

Hyderabad, Bengaluru, Pune +2

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Frequently asked questions

Which companies hire Java Full Stack with React professionals in Chennai?

Companies with large offices in Chennai include TCS, Infosys, Wipro, Cognizant, Capgemini, HCLTech, Tech Mahindra, LTIMindtree, Barclays, Walmart. Use their company pages below to practise employer-specific sets.

Are Java Full Stack with React interviews in Chennai different from other cities?

The questions depend more on the company than the city. Chennai's mix of employers decides the style: Many companies here hire freshers in large batches and train them on the job

How do I find Java Full Stack with React jobs in Chennai?

Shortlist companies with Chennai offices, keep your CV focused on Java Full Stack with React projects, apply on company career pages and job portals with the Chennai filter, and practise the questions on this page before each interview.

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