CoinSwitch Front end Developer Interview Questions and Answers

Q1. Explain OOPS Concept ?
Ans. 
OOPS (Object-Oriented Programming) is a programming paradigm based on the concept of objects, which can contain data and code.
• OOPS focuses on creating objects that interact with each other to solve problems.

• It involves concepts like classes, objects, inheritance, polymorphism, and encapsulation.

• For example, a class 'Car' can have objects like 'Toyota', 'Honda', etc., each with their own properties and methods.

• Inheritan...read more
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Round duration - 30 minutes
Round difficulty - Easy

Basic questioning about my work experiences, things I have developed and created, my work experience(internships). The challenges which I have faced and how I overcame them. Basic questions about some android concepts

Q1. What puzzles were asked during the interview, and can you describe the projects you discussed?
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Round duration - 45 minutes
Round difficulty - Medium

The interviewer was very friendly and asked about various things and tried to judge my understanding of the projects and how deep I know about the concepts I have implemented in my projects

Q1. RxJava
RxJava
Ans. 
RxJava is a popular library for composing asynchronous and event-based programs using observable sequences.
• RxJava provides a functional API for working with asynchronous data streams.

• It uses Observables to emit items and notify subscribers.

• Operators can be used to transform, filter, and combine these streams of data.

• Schedulers are used to control the threading behavior of these operations.

• Example: Creating an Observabl...read more
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Round duration - 40 minutes
Round difficulty - Medium

This was a system design round

Q1. Can you explain the fragment lifecycle in Android system design?
Ans. 
Fragment lifecycle in Android involves various states and methods for managing UI components.
• Fragments have several lifecycle states such as created, started, resumed, paused, stopped, and destroyed.

• Methods like onCreate(), onCreateView(), onResume(), onPause(), onStop(), onDestroy() are used to manage fragment lifecycle.

• Fragment lifecycle is closely tied to the hosting Activity's lifecycle.

• Example: When a fragment is ...read more
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Implement some LLD and use clean code formulas

Better be prepared for all deep dive questions about tech and project you worked

There was aptitude test out of which 12 candidate selected

Q1. Asked me about my project in details
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Q2. What does group by do in SQL.
Ans. 
GROUP BY in SQL is used to group rows that have the same values into summary rows.
• GROUP BY is used with aggregate functions like COUNT, SUM, AVG, etc.

• It is used to summarize data by grouping rows based on specified columns.

• GROUP BY is often used in conjunction with the SELECT statement.
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Q3. Then asked about spring boot
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Hacker rank test, with a medium level Data Structure problem

Q1. This round was specific to Javascript.
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Q2. Asked, Function currying, closure, hoisting, promise
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Q1. Designing round, where I was asked to built a feature with React. Also asked Javascript problems
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Q1. Web performance mechanism and how can I optimise the performance, these questions were asked
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Q2. Build a websocket, and questions about React JS
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Q1. Create Observer class
Ans. 
Create an Observer class
• Observer class is used to notify changes to multiple objects

• It maintains a list of objects that need to be notified

• It has methods to add, remove and notify observers

• Example: Weather station notifying multiple displays
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Q2. Create Pagination component similar to mui component
Ans. 
Create a pagination component similar to mui component.
• Use React to create a reusable pagination component

• Include props for total number of pages, current page, and page size

• Use Material UI styles for consistent look and feel

• Add event handlers for page changes

• Test component thoroughly
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Q1. Basic getting to know you and your background
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Pitch an idea to the CEO whether to solve for 5 min grocery delivery or not