Paytm Money Sdet Engineer Interview Questions and Answers for Experienced

Ajax calls allow for asynchronous communication between client and server without reloading the page.

• Ajax stands for Asynchronous JavaScript and XML

• Uses XMLHttpRequest object to send and receive data

• Allows for partial page updates without reloading the entire page

• Can handle data in various formats such as JSON, XML, HTML, and plain text

• Example: $.ajax({url: 'example.com', success: function(data){console.log(data)}});

REST is lightweight and uses HTTP while SOAP is XML-based and has more features.

• REST uses HTTP methods like GET, POST, PUT, DELETE while SOAP uses XML messaging.

• REST is stateless while SOAP can maintain state.

• REST is faster and easier to use while SOAP is more secure and reliable.

• REST is used for web services while SOAP is used for enterprise-level services.

• Example of REST: Twitter API. Example of SOAP: Amazon Web Serv

GET and POST are HTTP methods used for sending data to a server.

• GET is used to retrieve data from a server

• POST is used to submit data to a server

• GET requests can be cached and bookmarked

• POST requests are not cached and cannot be bookmarked

• GET requests have length restrictions

• POST requests have no length restrictions

• GET requests are less secure than POST requests

Observer pattern is a design pattern in which an object maintains a list of its dependents and notifies them automatically of any state changes.

• Also known as publish-subscribe pattern

• Used in event-driven systems

• Allows loose coupling between objects

• Example: A weather station broadcasts weather updates to multiple displays

• Example: A stock market ticker notifies multiple investors of stock price changes

Singleton is a design pattern that restricts the instantiation of a class to a single object.

• Singleton ensures that only one instance of a class exists in the entire application.

• It provides a global point of access to the instance.

• Commonly used in scenarios where a single instance needs to coordinate actions across the system.

• Example: Database connection manager, logger, configuration manager.

Immutable in Java refers to objects whose state cannot be changed after creation.

• String, Integer, and other wrapper classes are immutable in Java.

• Immutable objects are thread-safe and can be shared without synchronization.

• To create an immutable class, make all fields final and private, and don't provide setters.

• Examples of immutable classes in Java include LocalDate, LocalTime, and LocalDateTime.

Creating immutable in Java

• Use final keyword to make variables immutable

• Use private constructor to prevent object modification

• Use defensive copying to prevent modification of mutable objects

• Use enum to create immutable objects

• Use String class to create immutable strings

Dependency injection is a design pattern that allows objects to receive dependencies rather than creating them internally.

• It helps to decouple the code and makes it more testable and maintainable.

• It allows for easier swapping of dependencies without changing the code.

• There are three types of dependency injection: constructor injection, setter injection, and interface injection.

• Example: Instead of creating a database co...read more

CORS stands for Cross-Origin Resource Sharing. It is a security feature implemented in web browsers to restrict access to resources from different origins.

• CORS allows web servers to specify which origins are allowed to access its resources

• It is implemented using HTTP headers

• CORS prevents malicious websites from accessing sensitive data from other websites

• Examples of resources that may be restricted by CORS include cook

CORS can be overcome by configuring the server to allow cross-origin requests.

• Configure the server to include the Access-Control-Allow-Origin header

• Use JSONP (JSON with Padding) to bypass CORS restrictions

• Use a proxy server to make the request on behalf of the client

• Use a browser extension to disable CORS restrictions during development

• Use a server-side proxy to forward requests to the target server

Implement Binary Search Tree using given array of strings.

• Sort the array in ascending order

• Find the middle element and make it the root of the tree

• Recursively create left and right subtrees using the left and right halves of the array

• Repeat until all elements are added to the tree

Print the given Binary search tree in ascending order

• Traverse the left subtree recursively

• Print the root node

• Traverse the right subtree recursively

Find buy and sell points for maximum profit in an array of stock prices in O(n)

• Iterate through the array and keep track of the minimum price seen so far

• Calculate the profit at each index by subtracting the minimum price from the current price

• Update the maximum profit and buy/sell points accordingly

• Return the buy and sell points for maximum profit

Chennai faces problems related to water scarcity, traffic congestion, and pollution.

• Water scarcity due to inadequate rainfall and poor management of water resources.

• Traffic congestion due to the increasing number of vehicles and poor road infrastructure.

• Pollution caused by industries, vehicular emissions, and improper waste disposal.

Need more context on the question to provide an answer.

• Please provide more information on the problem to be solved.

• Without context, it is difficult to provide a solution.

• Can you please provide more details on the problem statement?

Visa is a global payments technology company that connects consumers, businesses, banks and governments in more than 200 countries and territories.

• Visa operates the world's largest retail electronic payments network.

• VisaNet, the company's global processing system, handles more than 65,000 transaction messages a second.

• Visa is constantly innovating to improve payment security and convenience, with initiatives such as Vi...read more