PhonePe Lead Software Engineer Interview Questions and Answers

Q1. What is collection framework?
Ans. 
Collection framework is a unified architecture for representing and manipulating collections of objects in Java.
• It provides interfaces (like List, Set, Map) and classes (like ArrayList, HashSet, HashMap) to store and manipulate groups of objects.

• It allows for easy manipulation, sorting, searching, and iteration of collections.

• Collections in the framework can store objects of any type, including user-defined classes.

• Exa...read more
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Q2. What is spring boot dependency injection?
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Spring Boot dependency injection is a design pattern where objects are passed their dependencies rather than creating them internally.
• In Spring Boot, dependency injection is achieved through the use of @Autowired annotation.

• It helps in achieving loose coupling between classes and promotes easier testing and maintenance.

• Example: @Autowired private UserService userService; // Injecting UserService dependency
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Q3. What is the use of rate limiter?
Ans. 
Rate limiter is used to control the rate of incoming requests to a server or API.
• Prevents server overload by limiting the number of requests a client can make in a specific time period

• Helps protect against DDoS attacks by limiting the rate of incoming requests

• Ensures fair usage of resources by preventing one client from monopolizing server resources

• Can be implemented using algorithms like token bucket or leaky bucket

• Ex...read more
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Q4. What is the mean by thread, how many ways we can create thread?
Ans. 
A thread is a lightweight sub-process that allows concurrent execution within a process. Threads can be created in multiple ways.
• Threads can be created by extending the Thread class in Java.

• Threads can be created by implementing the Runnable interface in Java.

• Threads can be created using thread pools in Java.

• Threads can be created using asynchronous functions in JavaScript.
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Q5. What is use of thread.join()?
Ans. 
thread.join() is used to wait for a thread to finish its execution before moving on to the next steps.
• thread.join() blocks the current thread until the thread it is called on completes its execution.

• It is commonly used in multi-threaded applications to ensure that all threads have finished before proceeding.

• Without thread.join(), the main thread may continue executing while other threads are still running.

• Example: thre...read more
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Q6. What is the difference between sync and asynchronous call?
Ans. 
Sync call blocks the execution until the response is received, while asynchronous call allows the program to continue executing without waiting for the response.
• Sync call blocks the program execution until the response is received

• Asynchronous call allows the program to continue executing without waiting for the response

• Sync calls are easier to understand and debug, but can lead to performance issues if used excessively

• ...read more
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Q7. How to deploy your service in production server?
Ans. 
Deploying service in production server involves building the application, configuring the server, and monitoring performance.
• Build the application code into a deployable package (e.g. JAR file for Java applications)

• Configure the production server with necessary dependencies and environment variables

• Deploy the application package to the server using tools like Docker, Kubernetes, or manual deployment scripts

• Monitor the ...read more
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Q8. What is use of Jenkins and kubernates?
Ans. 
Jenkins is a continuous integration tool used for automating software development processes, while Kubernetes is a container orchestration platform for managing containerized applications.
• Jenkins is used for automating the building, testing, and deployment of software projects.

• Kubernetes helps in automating the deployment, scaling, and management of containerized applications.

• Jenkins can be integrated with Kubernetes t...read more
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Q9. What is the difference between fail safe and fail fast
Ans. 
Fail safe focuses on ensuring system stability and preventing catastrophic failures, while fail fast prioritizes quick detection and response to errors.
• Fail safe is about designing systems to minimize the impact of failures and ensure stability.

• Fail fast is about quickly detecting and responding to errors to prevent further issues.

• Fail safe often involves redundancy and error checking mechanisms to prevent catastrophic...read more
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Q1. Describe the web application architecture.
Ans. 
Web application architecture refers to the structure and layout of components in a web application.
• Web application architecture typically consists of client-side and server-side components.

• Client-side components include the user interface and any client-side scripts.

• Server-side components include the server, application logic, and database.

• Common architectures include MVC (Model-View-Controller) and microservices.

• Examp...read more
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Q1. Search in a sorted matrix
Ans. 
Search for a target value in a sorted matrix efficiently.
• Start from the top right corner and move left or down based on comparison with target value

• Utilize the sorted nature of the matrix to eliminate certain rows or columns

• Implement binary search for more efficient search in each row or column
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Q2. Rotting orange graph
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Q3. Database Indexing and SQL
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Q1. Design Patterns
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Q2. Medium level Binary tree question
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Q3. Previous work discussion
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A test that covers all fundamental topics, including networking, object-oriented programming (OOP), and data structures and algorithms (DSA).

Q1. Write code for quick sort
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Q2. Puzzle
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Data structures and algo. 2 ques were asked in hackerrank

Q1. Questions related to System design
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Q1. Basic question related to Spring and Java
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It was a coding round of ReactJS and JS

Q1. Design Stopwatch in HTML CSS and JS
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Q1. LLD/Machine coding - Design a social media application with users, posts, comments, likes, etc. There is also an admin who needs to approve post creation and can delete any post they want. Create appropria...read more
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Q1. High-level design - Design a chat-based application like WhatsApp with only user-to-user chat feature (no group chats). Explain and draw out the E2E design by mentioning all the components and design decis...read more
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Q1. Hiring Manager - basic questions like why Razorpay, what are your career goals, what does career growth look like for you, etc.
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