Tech Mahindra Web Development Interview Questions & Answers
Curated interview practice questions with answers. These are practice scenarios, not a verified list of past interview questions.
About Tech Mahindra hiring for Web Development roles
Tech Mahindra is an Indian IT services and consulting company and part of the Mahindra Group. It is known for its strong telecom and communications practice and also serves banking, manufacturing and healthcare clients. In India it hires for software engineers, test engineers, network engineers, data analysts and data engineers.
For Web Development roles, this Tech Mahindra practice set focuses most on PHP Programming (7), MySQL Database (6), CSS Layout and Responsive Design (5), JavaScript Core (4). It has 13 easy, 17 medium questions, so you can start easy and work up to the harder ones.
Company type
IT services
Headquarters
Pune, India
Main India offices
Pune, Hyderabad, Bengaluru, Noida, Chennai
Tech Mahindra Web Development interview process
Online assessment (aptitude + English essay)
Coding test
Technical interview
HR round
Typical pattern based on public candidate experiences. Rounds vary by role, team and year.
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01
What is the difference between a primary key and a foreign key?
A primary key uniquely identifies each row in a table and cannot be NULL, for example students.id. A foreign key is a column in another table that refers to that primary key, such as enrollments.student_id, and enforces referential integrity so you cannot add an enrollment for a student who does not exist. Foreign keys can define ON DELETE CASCADE or RESTRICT behaviour. InnoDB supports foreign keys.
02
What is the difference between null and undefined?
undefined means a variable was declared but not assigned, a missing function argument, or a property that does not exist. null is an intentional empty value set by the developer, like clearing a selected user. typeof undefined is 'undefined', while typeof null is 'object', a long-standing quirk. APIs often return null for 'no data', and optional chaining like user?.address handles both safely.
03
Explain database normalization up to third normal form.
Normalization reduces duplicate data and update problems. 1NF requires atomic values, no repeating groups like phone1, phone2. 2NF requires every non-key column to depend on the whole primary key, not part of a composite key. 3NF removes transitive dependencies, so a column depends only on the key, for example moving city details out of an orders table. Read-heavy reports sometimes denormalise deliberately for speed.
Add loading='lazy' so the browser fetches them only when they come near the viewport:
<img src='gallery-1.jpg' alt='Campus' width='600' height='400' loading='lazy'>
<iframe src='https://www.youtube.com/embed/xyz' loading='lazy' title='Demo video'></iframe>
Do not lazy load the main hero or above-the-fold image, because that delays Largest Contentful Paint. For the hero use fetchpriority='high' instead, and always set width and height to avoid layout shift.
05
What is SQL injection and how do prepared statements stop it?
SQL injection happens when user input is concatenated into a query, so input like ' OR '1'='1 changes the query's logic and can dump or delete data. Prepared statements send the SQL structure and the data separately, so the database always treats input as a value, never as code. Escaping functions are not a full substitute. Least-privilege database users limit the damage if a flaw slips through.
06
What is PHP and how does a PHP page get processed?
PHP is a server-side scripting language widely used for websites, WordPress, Laravel apps and APIs. When a browser requests a .php file, the web server such as Apache or Nginx passes it to the PHP interpreter, usually through PHP-FPM. PHP runs the code, talks to databases if needed, and sends back plain HTML or JSON. The browser never sees the PHP source, only the generated output.
07
What is the difference between pseudo-classes and pseudo-elements?
A pseudo-class selects an element in a particular state, such as :hover, :focus, :nth-child(2) or :checked, and uses a single colon. A pseudo-element styles a specific part of an element or inserts generated content, such as ::before, ::after, ::first-line or ::placeholder, and uses a double colon. For example, a::after can add an arrow icon after links without extra HTML.
08
You changed DNS to a new server but some users still see the old site. Why?
DNS resolvers and browsers cache records for the TTL period, so changes propagate gradually; with a high TTL like 24 hours, some users keep the old IP for a day. I would check with dig or an online DNS checker from several locations. Best practice is lowering the TTL to 300 seconds a day before migration, keeping the old server running until traffic drains, and then raising the TTL again.
09
What is the difference between DELETE, TRUNCATE and DROP?
DELETE removes selected rows using a WHERE clause, can be rolled back inside a transaction and fires triggers, but is slow on large tables. TRUNCATE removes all rows quickly by recreating the table, resets AUTO_INCREMENT and cannot be rolled back in MySQL. DROP removes the table structure and data completely. Always take a backup and double-check the WHERE clause before running DELETE on production.
10
What is CORS and why does the browser block some API calls?
The same-origin policy stops scripts on one origin from reading responses from another origin. CORS is how a server opts in: it returns headers like Access-Control-Allow-Origin naming allowed origins. For non-simple requests, such as JSON with custom headers, the browser first sends an OPTIONS preflight. CORS is enforced only by browsers, so it is not a security control for the server itself, and Allow-Origin * should never be combined with credentials.
MVC separates an application into Models for data and business rules, Views for presentation, and Controllers that handle requests and connect the two. In Laravel, routes send a request to a controller, the controller uses Eloquent models to query the database, and returns a Blade view or JSON. This separation makes code testable and lets frontend and backend developers work on different layers without conflicts.
12
What is the difference between var, let and const?
var is function-scoped, is hoisted and initialised as undefined, and can be redeclared, which causes bugs in loops and blocks. let and const are block-scoped and sit in the temporal dead zone until their declaration line runs. let allows reassignment, while const does not, although objects declared with const can still have their properties changed. Modern code uses const by default and let only when the value must change.
13
Create students, courses and enrollments tables with proper keys.
A many-to-many relationship needs a junction table:
CREATE TABLE students (
id INT AUTO_INCREMENT PRIMARY KEY,
name VARCHAR(100) NOT NULL,
email VARCHAR(150) NOT NULL UNIQUE
);
CREATE TABLE courses (
id INT AUTO_INCREMENT PRIMARY KEY,
title VARCHAR(150) NOT NULL
);
CREATE TABLE enrollments (
student_id INT,
course_id INT,
enrolled_on DATE NOT NULL,
PRIMARY KEY (student_id, course_id),
FOREIGN KEY (student_id) REFERENCES students(id) ON DELETE CASCADE,
FOREIGN KEY (course_id) REFERENCES courses(id)
);
14
Tell me about a time you had to work with messy legacy code.
Situation: I joined a project with a 10-year-old PHP codebase full of mixed HTML and SQL. Task: I needed to add online payments without breaking existing features. Action: I wrote tests around the checkout flow first, extracted database code into a small class using PDO, and added the payment module separately. Result: payments launched with no regressions, and the team adopted the same approach for later changes.
15
What is the difference between px, em and rem units?
px is a fixed unit. em is relative to the font size of the current element, so nested em values compound and can grow unexpectedly. rem is relative to the root html font size, usually 16 pixels, so 1.5rem is always 24 pixels unless the user changes browser settings. Using rem for font sizes and spacing respects user preferences and keeps scaling consistent across the site.
16
Create a responsive card grid that needs no media queries.
auto-fit with minmax lets the grid decide how many columns fit:
.cards {
display: grid;
grid-template-columns: repeat(auto-fit, minmax(250px, 1fr));
gap: 1.5rem;
}
Each card is at least 250 pixels wide and the extra space is shared equally. On a phone it shows one column, on a tablet two and on a desktop three or four, all from three lines of CSS.
WHERE filters individual rows before grouping and cannot use aggregate functions. HAVING filters groups after GROUP BY and can use aggregates. For example, SELECT city, COUNT(*) FROM students WHERE status = 'active' GROUP BY city HAVING COUNT(*) > 50 first keeps only active students, then shows cities with more than 50 of them. Filtering in WHERE when possible is faster because fewer rows are grouped.
18
Users get logged out immediately after login when redirected. What could be wrong?
Likely causes are session_start() missing on the next page, output sent before session_start so headers fail, or the session cookie being dropped. Cookie issues include a Secure flag on an HTTP site, a domain mismatch between www and non-www, or SameSite settings during cross-site redirects. I would check the Set-Cookie header in DevTools, verify session.save_path is writable, and redirect to a single canonical domain.
19
What is the difference between DOMContentLoaded and the load event?
DOMContentLoaded fires when the HTML has been fully parsed and the DOM is built, without waiting for images, stylesheets or iframes. load fires on window only after every resource, including images, has finished loading. Most scripts that attach listeners should run on DOMContentLoaded, or simply use defer. load is useful when you need image dimensions or must start something after everything is ready.
20
What is the difference between sessions and cookies in PHP?
A cookie stores data in the browser and is sent with every request, so users can see and edit it. A session stores data on the server and keeps only a session id in a cookie, usually PHPSESSID. Use $_SESSION for login state and cart data, after calling session_start(). Use cookies only for non-sensitive preferences, and mark session cookies HttpOnly, Secure and SameSite.
A simple scripted deployment:
ssh deploy@server.example.com << 'EOF'
cd /var/www/app
git pull origin main
composer install --no-dev --optimize-autoloader
php artisan migrate --force
php artisan config:cache
sudo systemctl reload php8.3-fpm
EOF
Use an SSH key, not a password, and a non-root deploy user. Reloading PHP-FPM clears OPcache so new code is served. For safer releases, deploy into a new folder and switch a symlink.
Set cookie parameters before session_start:
session_set_cookie_params([
'lifetime' => 0,
'path' => '/',
'secure' => true,
'httponly' => true,
'samesite' => 'Lax'
]);
ini_set('session.use_strict_mode', '1');
session_start();
secure sends the cookie only over HTTPS, httponly hides it from JavaScript so XSS cannot steal it, and SameSite reduces CSRF. Strict mode rejects session ids the server never created.
23
Remove duplicates from an array of numbers and from an array of objects.
For primitives, a Set is simplest; for objects, use a Map keyed by id:
const nums = [1, 2, 2, 3, 3];
const unique = [...new Set(nums)];
const users = [{ id: 1 }, { id: 2 }, { id: 1 }];
const uniqueUsers = [
...new Map(users.map(u => [u.id, u])).values()
];
Both are O(n). A Set compares objects by reference, so it cannot remove two different objects with the same id.
When vertical margins of adjacent block elements touch, they merge into a single margin equal to the larger one instead of adding up. It also happens between a parent and its first or last child when no padding, border or block formatting context separates them. Margins do not collapse in flex or grid containers. Developers often avoid surprises by using padding, gap or margin in one direction only.
25
What is the difference between a shallow copy and a deep copy?
A shallow copy, made with spread syntax or Object.assign, copies only top-level properties, so nested objects are still shared references. Changing copy.address.city also changes the original. A deep copy duplicates every nested level. Modern browsers and Node provide structuredClone(obj), which handles dates, maps and circular references. JSON.parse(JSON.stringify(obj)) also works but drops functions, undefined and converts dates to strings.
26
Create a dark mode toggle that remembers the user's choice.
Store the choice in localStorage and apply it on load:
const root = document.documentElement;
const saved = localStorage.getItem('theme');
if (saved) root.dataset.theme = saved;
toggle.addEventListener('click', () => {
const next = root.dataset.theme === 'dark' ? 'light' : 'dark';
root.dataset.theme = next;
localStorage.setItem('theme', next);
toggle.setAttribute('aria-pressed', next === 'dark');
});
Running the first lines in a small inline script in the head avoids a flash of the wrong theme.
27
Center a div horizontally and vertically using Flexbox and Grid.
Both methods work on the parent container:
.parent-flex {
display: flex;
justify-content: center;
align-items: center;
min-height: 100vh;
}
.parent-grid {
display: grid;
place-items: center;
min-height: 100vh;
}
place-items is shorthand for align-items and justify-items. Using min-height instead of height lets content grow without overflowing on small screens.
28
How did string and number comparison with == change in PHP 8?
Before PHP 8, comparing a number with a non-numeric string converted the string to a number, so 0 == 'abc' was true, which caused security bugs. Since PHP 8, if the string is not numeric, the number is converted to a string and compared as strings, so 0 == 'abc' is now false. Using === is still recommended because it checks type and value without any conversion.
29
The database server is overloaded by read traffic. What architecture changes would you suggest?
I would first add caching for frequent reads with Redis or application-level caching. Then I would set up one or more read replicas and route SELECT queries to them while writes go to the primary, keeping replication lag in mind for read-after-write cases. Optimising slow queries and indexes often gives the cheapest wins. Managed services like Amazon RDS make adding replicas straightforward.
30
What is Composer and how does PSR-4 autoloading work?
Composer is PHP's dependency manager. composer.json lists packages, composer.lock pins exact versions, and the vendor folder holds installed code. PSR-4 maps a namespace prefix to a folder, for example App\ to src/, so App\Models\User loads from src/Models/User.php automatically after you require vendor/autoload.php. This removes manual require statements. composer.lock should be committed so every environment installs identical versions.
Tips to crack the Tech Mahindra Web Development interview
Read about telecom basics like 4G, 5G and network operations, since communications is Tech Mahindra's largest vertical.
Practise English essay and verbal ability sections, which often appear in Tech Mahindra online assessments.
Revise SQL and one programming language, and prepare a clear two-minute explanation of your project.
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; Tech Mahindra interviewers usually ask follow-ups on your first answer.
Frequently asked questions
How many rounds are there in the Tech Mahindra Web Development interview?
Candidates usually go through 4 stages: Online assessment (aptitude + English essay); 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 Tech Mahindra Web Development interview?
This practice set leans on PHP Programming (7), MySQL Database (6), CSS Layout and Responsive Design (5), JavaScript Core (4). Revise those first, then practise explaining one or two of your own projects end to end, because most Tech Mahindra interviewers ask you to walk through real work.
Are these the exact questions asked at Tech Mahindra?
No. These are curated practice questions that match the skills and difficulty usually tested in it services interviews like Tech Mahindra's. They are not a leaked or verified list of past questions.
Where does Tech Mahindra hire Web Development professionals in India?
Tech Mahindra has large teams in Pune, Hyderabad, Bengaluru, Noida, Chennai. Openings and locations change often, so check the Tech Mahindra careers page and filter by city and experience.