LTIMindtree Java Full Stack with React Interview Questions & Answers
Curated interview practice questions with answers. These are practice scenarios, not a verified list of past interview questions.
About LTIMindtree hiring for Java Full Stack with React roles
LTIMindtree is an Indian IT services and consulting company formed by the merger of Larsen and Toubro Infotech and Mindtree, and part of the L&T Group. It provides cloud, data, ERP, testing and digital engineering services for global clients. It hires for software engineers, test engineers, data analysts, data engineers and ERP consultants.
For Java Full Stack with React roles, this LTIMindtree practice set focuses most on Core Java (5), JavaScript, HTML and CSS (5), REST APIs, Security and Microservices (5), SQL and Databases (4). It has 16 easy, 13 medium, 1 hard questions, so you can start easy and work up to the harder ones.
Company type
IT services
Headquarters
Mumbai, India
Main India offices
Mumbai, Pune, Bengaluru, Chennai, Hyderabad
LTIMindtree Java Full Stack with React interview process
Online assessment (aptitude + reasoning)
Coding test
Technical interview
HR round
Typical pattern based on public candidate experiences. Rounds vary by role, team and year.
Solved for LTIMindtreeStart practicing
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INNER JOIN returns only rows that match in both tables. LEFT JOIN returns all rows from the left table plus matches from the right, with nulls where there is no match. RIGHT JOIN is the reverse. FULL OUTER JOIN returns all rows from both sides, which MySQL does not support directly. CROSS JOIN returns every combination. A self join joins a table to itself, such as employees and their managers.
02
You are passing the same user prop through five levels of components. What would you do?
This is prop drilling, which makes intermediate components depend on data they do not use. For global, rarely changing data like the logged-in user or theme, create a context with a provider at the top and read it with useContext through a custom hook such as useAuth. Alternatively, use component composition, passing ready-made elements as children. For complex shared state, a store like Zustand or Redux Toolkit is suitable.
03
What is the difference between == and equals() in Java?
The == operator compares references for objects, meaning it checks whether two variables point to the same object in memory. equals() compares logical content when a class overrides it, as String, Integer and most collections do. For example, new String("a") == new String("a") is false but equals() returns true. For primitives, == compares values. Always use equals() for objects and Objects.equals(a, b) to stay null-safe.
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.
05
What is the difference between localStorage, sessionStorage and cookies?
localStorage keeps data with no expiry for the origin, around 5 to 10 MB, and is shared across tabs. sessionStorage is similar but cleared when the tab closes and is per tab. Cookies are small, around 4 KB, are sent automatically with every request to the server and can be marked HttpOnly, Secure and SameSite. Use cookies for auth sessions, and storage for non-sensitive UI preferences only, since scripts can read storage.
function debounce(fn, delay = 300) {
let timer;
return function (...args) {
clearTimeout(timer);
timer = setTimeout(() => fn.apply(this, args), delay);
};
}
const search = debounce(term => {
fetch(`/api/products?q=${encodeURIComponent(term)}`);
}, 400);
input.addEventListener('input', e => search(e.target.value));
// Only the last call within 400 ms actually runs.
07
Write a record and use pattern matching in a switch expression.
Avoid streaming large files through the application server. Generate a pre-signed URL for object storage like S3 or Azure Blob so the browser uploads directly, then the client calls the API to confirm and save the metadata. If uploads must go through Spring, raise spring.servlet.multipart.max-file-size, stream the input to storage instead of loading it into memory, validate type and size, and scan files for malware before use.
09
You need H2 for local development, MySQL for testing and PostgreSQL in production. How do you configure this?
Create application-dev.yml, application-test.yml and application-prod.yml, each with its own spring.datasource URL, username and driver. Keep shared settings in application.yml. Activate the right one with SPRING_PROFILES_ACTIVE in each environment. Read production credentials from environment variables, for example url: ${DB_URL}, instead of hard-coding them. For realistic integration tests, Testcontainers can start the same database engine used in production.
10
Your application logs show database deadlock errors during peak hours. How do you resolve them?
A deadlock happens when two transactions lock rows in opposite order and wait for each other; the database kills one. Read the deadlock report, such as SHOW ENGINE INNODB STATUS, to find the statements. Fix by updating rows in a consistent order, keeping transactions short, avoiding user interaction or remote calls inside transactions and adding indexes so updates lock fewer rows. Also add a retry for the deadlock error because occasional ones are normal.
11
What is a closure in JavaScript? Give a practical use.
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.
12
Build a login form with basic validation in React.
During compilation, declarations are moved to the top of their scope. Function declarations are hoisted fully, so they can be called before they appear. var declarations are hoisted and initialised to undefined. let, const and class declarations are hoisted but stay uninitialised in the temporal dead zone, so accessing them early throws a ReferenceError. Function expressions assigned to variables follow the variable's rules.
A List is an ordered collection that allows duplicates and index access, such as ArrayList. A Set holds unique elements; HashSet has no order, LinkedHashSet keeps insertion order and TreeSet keeps elements sorted. A Map stores key-value pairs with unique keys, such as HashMap or TreeMap, and is not part of the Collection interface. Choose based on whether you need duplicates, ordering or lookup by key.
15
Write global exception handling for a REST API in Spring Boot.
Authentication verifies who the user is, for example by checking a password, OTP or token. Authorization decides what that authenticated user is allowed to do, for example only admins can delete products. In Spring Security, authentication produces an Authentication object with granted authorities, and authorization uses those authorities in URL rules or annotations like @PreAuthorize("hasRole('ADMIN')"). A failed authentication gives 401 and a failed authorization gives 403.
17
You are loading about five lakh records into an ArrayList and a HashMap and memory spikes during loading. What can you do?
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.
18
The application fails with NoSuchBeanDefinitionException for a service. How do you debug it?
Check that the class has @Service or @Component, or is created by a @Bean method. Make sure it is inside the package of the main @SpringBootApplication class or a scanned sub-package. If there are several implementations, use @Qualifier or @Primary. Also check @Profile or @Conditional annotations that may disable it in the current environment. Running with --debug prints the condition report that shows why a bean was not created.
Atomicity means a transaction fully succeeds or fully rolls back. Consistency means it moves the database from one valid state to another, respecting constraints. Isolation means concurrent transactions do not see each other's partial work. Durability means committed data survives crashes, thanks to write-ahead logs. A bank transfer that debits one account and credits another is the classic example where all four properties matter.
20
What is the N+1 select problem and how do you solve it?
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.
21
Your React app gets 403 Forbidden on POST requests to Spring Boot, but GET works. What is the likely cause?
With Spring Security enabled, CSRF protection is on by default and blocks POST, PUT and DELETE that lack a CSRF token, while GET is allowed. For a stateless JWT API, disable CSRF in the SecurityFilterChain. If you use session cookies, keep CSRF and send the token with CookieCsrfTokenRepository. Also check CORS, because a rejected preflight OPTIONS request or a missing role in authorization rules can produce the same symptom.
ArrayList is backed by a resizable array, giving O(1) random access and good cache locality, and appending is amortised O(1). LinkedList is a doubly linked list with O(1) insertion at known nodes but O(n) access by index and more memory per element. In practice ArrayList is faster for almost all workloads. For queue or stack behaviour, ArrayDeque is usually better than LinkedList.
23
Show how to read a file safely using try-with-resources.
Java 17 brought records for immutable data carriers, sealed classes to restrict inheritance, text blocks for multi-line JSON or SQL, and pattern matching for instanceof. Java 21, the current widely used LTS alongside 17, added virtual threads for cheap blocking concurrency, pattern matching for switch, record patterns and sequenced collections. Spring Boot 3 needs Java 17 or later, and from Boot 3.2 virtual threads can be enabled with one property.
25
Write a query to find duplicate email addresses in a users table and delete the extra rows.
-- Find duplicates
SELECT email, COUNT(*) AS cnt
FROM users
GROUP BY email
HAVING COUNT(*) > 1;
-- Keep the lowest id, delete the rest (MySQL / PostgreSQL)
DELETE FROM users u
USING users k
WHERE u.email = k.email
AND u.id > k.id; -- PostgreSQL syntax
-- Then add: ALTER TABLE users ADD CONSTRAINT ux_email UNIQUE (email);
final is a keyword: a final variable cannot be reassigned, a final method cannot be overridden and a final class cannot be extended. finally is a block after try or catch that always runs, used for cleanup, although try-with-resources is now preferred. finalize() was an Object method called before garbage collection; it is deprecated for removal because its timing is unpredictable. Use Cleaner or try-with-resources instead.
27
You need to store unique usernames and always display them in alphabetical order. Which collection do you pick?
A TreeSet fits because it rejects duplicates and keeps elements sorted using natural order or a Comparator, with O(log n) add and lookup. Use String.CASE_INSENSITIVE_ORDER as the comparator if Rahul and rahul should be treated as the same. If you only need sorting once at display time, a HashSet followed by sorting may be faster. For concurrent access, ConcurrentSkipListSet is the thread-safe sorted alternative.
28
Explain the common HTTP status codes a REST API should return.
200 OK for successful reads and updates, 201 Created with a Location header after creating a resource, and 204 No Content for successful deletes. 400 Bad Request for validation errors, 401 Unauthorized when authentication is missing or invalid, 403 Forbidden when the user is authenticated but not allowed, 404 Not Found, 409 Conflict for version or duplicate conflicts, and 429 Too Many Requests for rate limits. 500 means an unexpected server error and 503 means temporarily unavailable.
29
Why does React need a key prop when rendering lists?
Keys help React match list items between renders, so it knows which items were added, removed or moved. Use a stable unique ID from the data, such as product.id. Using the array index as key causes bugs when items are reordered or deleted, because state and input values can attach to the wrong row. Keys only need to be unique among siblings, and they are not passed to the component as a prop.
30
What roles do an API gateway and service discovery play in microservices?
An API gateway, such as Spring Cloud Gateway, is the single entry point for clients. It handles routing, authentication, rate limiting, CORS and request logging. Service discovery lets services find each other without hard-coded addresses: with Eureka or Consul, services register themselves, and clients look them up. On Kubernetes, built-in Services and DNS usually replace a separate discovery server, and an ingress or gateway handles external traffic.
Tips to crack the LTIMindtree Java Full Stack with React interview
Practise aptitude, logical reasoning and basic coding questions, as the online assessment is usually the first filter.
Revise SQL, OOP and testing fundamentals, plus any cloud or data tools you list on your resume.
Learn about the L&T Group background and the LTI and Mindtree merger to answer company-related questions.
Keep a one-minute story ready for every project on your CV: problem, your part, tools, result.
Practise the hard questions on this page aloud; LTIMindtree interviewers usually ask follow-ups on your first answer.
Frequently asked questions
How many rounds are there in the LTIMindtree Java Full Stack with React interview?
Candidates usually go through 4 stages: Online assessment (aptitude + reasoning); Coding test; Technical interview; HR round. The exact rounds change with the role, team, location and your experience, so confirm the process with the recruiter.
Which topics should I prepare for the LTIMindtree Java Full Stack with React interview?
This practice set leans on Core Java (5), JavaScript, HTML and CSS (5), REST APIs, Security and Microservices (5), SQL and Databases (4). Revise those first, then practise explaining one or two of your own projects end to end, because most LTIMindtree interviewers ask you to walk through real work.
Are these the exact questions asked at LTIMindtree?
No. These are curated practice questions that match the skills and difficulty usually tested in it services interviews like LTIMindtree's. They are not a leaked or verified list of past questions.
Where does LTIMindtree hire Java Full Stack with React professionals in India?
LTIMindtree has large teams in Mumbai, Pune, Bengaluru, Chennai, Hyderabad. Openings and locations change often, so check the LTIMindtree careers page and filter by city and experience.
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