Tech Mahindra Interview Questions and Answers for Freshers

JavaScript is a versatile, high-level programming language primarily used for web development to create interactive and dynamic web pages.

• JavaScript is an interpreted language, meaning it runs directly in the browser without needing compilation.

• It supports event-driven programming, allowing developers to create responsive user interfaces. Example: handling button clicks.

• JavaScript can manipulate the Document Object Mod...read more

React.js is a popular JavaScript library for building user interfaces, particularly single-page applications, using a component-based architecture.

• Component-Based: React allows developers to create reusable UI components, making code more modular and maintainable.

• Virtual DOM: React uses a virtual representation of the DOM to optimize rendering and improve performance.

• Unidirectional Data Flow: Data in React flows in one...read more

Node.js is a JavaScript runtime built on Chrome's V8 engine, enabling server-side scripting and building scalable network applications.

• Node.js uses an event-driven, non-blocking I/O model, making it efficient and suitable for I/O-heavy applications.

• It allows developers to use JavaScript on both the client and server sides, promoting code reuse.

• Node.js has a rich ecosystem of libraries and frameworks, such as Express.js...read more

CSS (Cascading Style Sheets) is a stylesheet language used to describe the presentation of a document written in HTML or XML.

• CSS controls layout, colors, fonts, and overall visual appearance of web pages.

• It allows for responsive design, enabling websites to adapt to different screen sizes (e.g., using media queries).

• CSS can be applied inline, embedded in the HTML document, or linked as an external stylesheet.

• Example of...read more

HTML (HyperText Markup Language) is the standard language for creating web pages and web applications.

• HTML uses tags to structure content, e.g., <h1> for headings, <p> for paragraphs.

• It allows embedding multimedia elements like images (<img>) and videos (<video>).

• HTML forms (<form>) enable user input, with elements like text fields (<input>) and buttons (<button>).

• HTML document...read more

Loops are programming constructs that repeat a block of code multiple times based on a condition.

• Types of loops: for, while, and do-while.

• For loop example: for (let i = 0; i < 5; i++) { console.log(i); }

• While loop example: let i = 0; while (i < 5) { console.log(i); i++; }

• Do-while loop example: let i = 0; do { console.log(i); i++; } while (i < 5);

• Loops help in automating repetitive tasks and iterating over data...read more

In JavaScript, 'obj' typically refers to an object, a fundamental data structure that holds key-value pairs.

• Objects are created using curly braces: const obj = {};

• They can hold various data types: const person = { name: 'Alice', age: 25 };

• Access properties using dot notation: console.log(person.name); // 'Alice'

• Use bracket notation for dynamic keys: const key = 'age'; console.log(person[key]); // 25

• Objects can also con...read more

A function is a reusable block of code that performs a specific task in programming.

• Functions can take inputs, known as parameters, and return outputs. Example: function add(a, b) { return a + b; }

• They help in organizing code, making it modular and easier to maintain.

• Functions can be defined using function declarations or function expressions.

• Example of a function expression: const multiply = function(x, y) { return x ...read more

An array is a data structure that stores a collection of elements, typically of the same type, in a contiguous memory location.

• Arrays can hold multiple values in a single variable, e.g., let fruits = ['apple', 'banana', 'cherry'];

• They are zero-indexed, meaning the first element is accessed with index 0, e.g., fruits[0] returns 'apple';

• Arrays can be of fixed or dynamic size, e.g., in Java, int[] numbers = new int[5]; cr...read more

Controlled components in web development manage form data through React state, ensuring predictable UI behavior.

• Controlled components use state to manage form inputs, e.g., <input value={this.state.value} onChange={this.handleChange} />.

• They provide a single source of truth for form data, making it easier to validate and manipulate inputs.

• Controlled components can be reset or modified programmatically, enhancing ...read more

CSS (Cascading Style Sheets) is a stylesheet language used to describe the presentation of HTML documents.

• CSS controls layout, colors, fonts, and overall visual appearance of web pages.

• It allows for responsive design, adapting layouts to different screen sizes (e.g., using media queries).

• CSS can be applied inline, embedded in the HTML, or linked as an external stylesheet.

• Example of a CSS rule: 'h1 { color: blue; font-s...read more

I have a strong background in customer service, excellent communication skills, and a passion for helping customers.

• Extensive experience in customer service roles

• Excellent communication skills

• Strong problem-solving abilities

• Passion for helping customers

• Proven track record of resolving customer issues efficiently

I am fluent in English, Hindi, and Spanish. I have knowledge about PhonePe's services and features.

• Fluent in English, Hindi, and Spanish

• Knowledge about PhonePe's services and features

• Experience in customer service roles

Query to find customer names with the maximum orders from Customers and Orders tables.

• Use JOIN to combine Customers and Orders tables on CustomerID.

• Group by CustomerID and count orders to find the maximum.

• Use a subquery to filter customers with the maximum order count.

• Example SQL: SELECT c.customerName FROM Customers c JOIN Orders o ON c.customerID = o.CustomerID GROUP BY c.customerID HAVING COUNT(o.OrderId) = (SELECT ...read more

The project involves building a data pipeline to ingest, process, and analyze large volumes of data from various sources in Azure.

• Utilizing Azure Data Factory for data ingestion and orchestration

• Implementing Azure Databricks for data processing and transformation

• Storing processed data in Azure Data Lake Storage

• Using Azure Synapse Analytics for data warehousing and analytics

• Leveraging Azure DevOps for CI/CD pipeline aut...read more

Designing an effective ADF pipeline involves considering various metrics and factors.

• Understand the data sources and destinations

• Identify the dependencies between activities

• Optimize data movement and processing for performance

• Monitor and track pipeline execution for troubleshooting

• Consider security and compliance requirements

• Use parameterization and dynamic content for flexibility

• Implement error handling and retries fo...read more

Optimize data processing by partitioning, indexing, and using efficient storage formats.

• Partitioning: Divide large datasets into smaller, manageable chunks. For example, partitioning a sales dataset by year.

• Indexing: Create indexes on frequently queried columns to speed up data retrieval. For instance, indexing customer IDs in a transaction table.

• Data Compression: Use compressed formats like Parquet or ORC to reduce st...read more

Use Slowly Changing Dimensions (SCD) to preserve historical data while reconstructing a table.

• Implement SCD Type 1 for overwriting old data without keeping history.

• Use SCD Type 2 to create new records for changes, preserving history.

• Example of SCD Type 2: If a customer's address changes, add a new record with the new address and mark the old record as inactive.

• SCD Type 3 allows for limited history by adding new columns...read more

Databricks enhances data processing with advanced analytics, collaboration, and scalability beyond ADF's capabilities.

• Databricks provides a collaborative environment for data scientists and engineers to work together using notebooks.

• It supports advanced analytics and machine learning workflows, which ADF lacks natively.

• Databricks can handle large-scale data processing with Apache Spark, making it more efficient for big...read more

Bigtable is a NoSQL database for real-time analytics, while BigQuery is a fully managed data warehouse for running SQL queries.

• Bigtable is a NoSQL database designed for real-time analytics and high throughput, while BigQuery is a fully managed data warehouse for running SQL queries.

• Bigtable is used for storing large amounts of semi-structured data, while BigQuery is used for analyzing structured data using SQL queries.

• ...read more

To remove duplicate rows from BigQuery, use the DISTINCT keyword. To find the month of a given date, use the EXTRACT function.

• To remove duplicate rows, use SELECT DISTINCT * FROM table_name;

• To find the month of a given date, use SELECT EXTRACT(MONTH FROM date_column) AS month_name FROM table_name;

• Make sure to replace 'table_name' and 'date_column' with the appropriate values in your query.

The operator used in Composer to move data from GCS to BigQuery is the GCS to BigQuery operator.

• The GCS to BigQuery operator is used in Apache Airflow, which is the underlying technology of Composer.

• This operator allows you to transfer data from Google Cloud Storage (GCS) to BigQuery.

• You can specify the source and destination parameters in the operator to define the data transfer process.

Code to square each element in the input array.

• Iterate through the input array and square each element.

• Store the squared values in a new array to get the desired output.

Dataflow is a fully managed stream and batch processing service, while Dataproc is a managed Apache Spark and Hadoop service.

• Dataflow is a serverless data processing service that automatically scales to handle your data, while Dataproc is a managed Spark and Hadoop service that requires you to provision and manage clusters.

• Dataflow is designed for both batch and stream processing, allowing you to process data in real-t...read more

BigQuery architecture includes storage, execution, and optimization components for efficient query processing.

• BigQuery stores data in Capacitor storage system for fast access.

• Query execution is distributed across multiple nodes for parallel processing.

• Query optimization techniques include partitioning tables, clustering tables, and using query cache.

• Using partitioned tables can help eliminate scanning unnecessary data.

• ...read more

RDD vs dataframe vs dataset in PySpark

• RDD (Resilient Distributed Dataset) is the basic abstraction in PySpark, representing a distributed collection of objects

• Dataframe is a distributed collection of data organized into named columns, similar to a table in a relational database

• Dataset is a distributed collection of data with the ability to use custom classes for type safety and user-defined functions

• Dataframes and Data...read more