Epsilon Lead Software Engineer Interview Questions and Answers for Experienced

Rate limit design involves setting limits on the number of requests a user can make within a certain time frame to prevent abuse or overload.

• Consider the type of requests being made and the impact of rate limiting on user experience.

• Implement rate limiting at different levels such as API endpoints, user accounts, or IP addresses.

• Use tokens or tokens buckets to track and enforce rate limits.

• Provide clear error messages ...read more

Program to print odd and even numbers using multithreading

• Create two separate threads for printing odd and even numbers

• Use synchronization mechanisms like mutex or semaphore to ensure proper ordering of output

• Example: Thread 1 prints odd numbers (1, 3, 5, ...) and Thread 2 prints even numbers (2, 4, 6, ...)

Routing is the process of selecting a path for network traffic to travel from one network to another.

• Routing is done by routers in a network.

• Types of routing include static routing, dynamic routing, and default routing.

• Static routing involves manually configuring the routes.

• Dynamic routing uses protocols to automatically update the routing table.

• Default routing is used when there is no specific route for a packet.

• Examp...read more

Factory design pattern is a creational pattern that provides an interface for creating objects in a superclass, but allows subclasses to alter the type of objects that will be created.

• Factory pattern is used when we have a superclass with multiple subclasses and based on input, we need to return one of the subclass.

• It provides a way to delegate the instantiation logic to child classes.

• Example: java.util.Calendar, java....read more

The current project is a web-based e-commerce platform with a microservices architecture.

• The project uses a combination of front-end technologies like React and back-end technologies like Node.js and Java.

• It follows a microservices architecture where different services handle specific functionalities like user management, product catalog, and order processing.

• The services communicate with each other through APIs and me...read more

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

• Dependency injection helps to decouple components and make them more modular.

• It allows for easier testing and maintenance of code.

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

• Example: Instead of creating a database connection object ...read more

Caching is the process of storing frequently accessed data in a temporary storage area for faster access.

• Caching reduces the time and resources required to access data.

• Types of caching include browser caching, server caching, and database caching.

• Browser caching stores web page resources like images, stylesheets, and scripts on the user's device.

• Server caching stores frequently accessed data on the server to reduce dat...read more

Web application is a complete software program accessed through a web browser, while web API application is a set of programming instructions that allow communication between different software systems.

• Web application is a complete software program accessed through a web browser

• Web API application is a set of programming instructions that allow communication between different software systems

• Web application provides a ...read more

Interfaces are contracts that define a set of methods that a class must implement. They help achieve abstraction and loose coupling.

• Interfaces provide a way to achieve abstraction and loose coupling in code.

• They define a set of methods that a class must implement, but not how they are implemented.

• Classes can implement multiple interfaces, allowing for greater flexibility and reusability.

• Interfaces are commonly used in ...read more

Load balancing is the process of distributing network traffic across multiple servers to avoid overloading a single server.

• Load balancing helps to improve the performance, availability, and scalability of applications.

• It can be achieved through hardware or software solutions.

• Examples of load balancing algorithms include round-robin, least connections, and IP hash.

• Load balancing can also be combined with other technique...read more

SSL is a security protocol used to establish an encrypted link between a web server and a browser.

• SSL stands for Secure Sockets Layer.

• It is used to protect sensitive information such as login credentials, credit card details, etc.

• SSL uses encryption to ensure that data transmitted between the server and browser cannot be intercepted by third parties.

• It is essential for e-commerce websites, online banking, and any websi...read more

Encryption is the process of converting plain text into a coded message to prevent unauthorized access.

• Encryption uses an algorithm and a key to convert plain text into ciphertext.

• Decryption uses the same algorithm and key to convert ciphertext back into plain text.

• Common encryption algorithms include AES, RSA, and Blowfish.

• Encryption is used to protect sensitive data such as passwords, credit card numbers, and persona...read more

CORS (Cross-Origin Resource Sharing) is a security feature that restricts web pages from making requests to a different domain.

• CORS issue occurs when a web page tries to access resources from a different domain

• It is a security feature implemented by web browsers to prevent cross-site scripting attacks

• CORS issue can be resolved by configuring the server to allow cross-origin requests or by using JSONP

• It can occur in AJA...read more

Indexes can slow down insert performance due to the overhead of maintaining the index.

• Inserting data into the table without indexes will be faster than inserting into the table with indexes.

• The more indexes a table has, the slower the insert performance will be.

• However, indexes can improve query performance by allowing the database to quickly find the data being searched for.

Ajax calls are asynchronous HTTP requests made by JavaScript to a server without reloading the page.

• Ajax stands for Asynchronous JavaScript and XML

• Used to update parts of a web page without reloading the entire page

• Can be used to fetch data from a server and display it on a web page

• Examples: Google Maps, Facebook News Feed

Angular is a popular front-end web application framework that uses TypeScript as its primary language.

• Angular is developed and maintained by Google.

• It is used for building dynamic, single-page web applications.

• It uses TypeScript, a superset of JavaScript, which adds features like static typing and class-based object-oriented programming.

• Angular provides a range of features like data binding, dependency injection, and c...read more

Lazy loading is a technique used to defer the loading of non-critical resources until they are actually needed.

• It improves page load time and performance.

• It reduces the initial load time of a web page.

• It is commonly used for images, videos, and other media files.

• It can be implemented using JavaScript or server-side scripting.

• Example: Images below the fold on a webpage are loaded only when the user scrolls down to them.