American Express L2 Engineer Interview Questions and Answers

Test was for Web Development - React
75min test
3 Questions
1 Coding Question
2 Scenario based questions

Q1. React Optimization techniques
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Q2. React Advantages
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Q1. How to debug in production environment?
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Q1. Challenges faced during work and how you overcome?
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Q1. Why you choose Wells fargo over other offers?
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Q1. Java difference between Finally, Finalize
Ans. 
Finally is a block of code that always executes, while Finalize is a method used for cleanup before an object is garbage collected.
• Finally block is used in exception handling to ensure certain code is always executed, regardless of whether an exception is thrown or not.

• Finalize method is called by the garbage collector before an object is reclaimed.

• Finally block is used in try-catch-finally blocks, while Finalize metho...read more
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Q2. Programming question - Find second largest string from a given sentence
Ans. 
Find the second largest string from a given sentence
• Split the sentence into an array of strings

• Sort the array based on string length

• Return the second last element in the sorted array
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Q3. Difference between AWS cloud front and cloud formation
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AWS CloudFront is a content delivery network (CDN) service, while AWS CloudFormation is an infrastructure as code service.
• CloudFront is used to deliver content to end users with low latency and high data transfer speeds.

• CloudFormation is used to automate the deployment of infrastructure resources in a repeatable and predictable manner.

• CloudFront is a CDN service that caches content at edge locations to reduce latency, ...read more
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Q4. How to improve performance in react js ?
Ans. 
To improve performance in React JS, optimize rendering, minimize re-renders, use virtualization, lazy loading, code splitting, and memoization.
• Optimize rendering by using shouldComponentUpdate or React.memo for functional components

• Minimize re-renders by using PureComponent or memoization techniques like useMemo or useCallback

• Use virtualization for long lists or tables to render only the visible items

• Implement lazy loa...read more
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Q1. What is list comprehension
Ans. 
List comprehension is a concise way to create lists in Python by applying an expression to each item in an iterable.
• List comprehension is written inside square brackets []

• It consists of an expression followed by a for clause, then zero or more if clauses

• Example: squares = [x**2 for x in range(10)]
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Q2. Explain spark architecture
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Apache Spark is a distributed computing system that provides an interface for programming entire clusters with implicit data parallelism and fault tolerance.
• Apache Spark follows a master-slave architecture with a driver program that communicates with a cluster manager to distribute work across worker nodes.

• It uses Resilient Distributed Datasets (RDDs) as the basic data structure, which are immutable distributed collect...read more
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Write code for palindtomr

1 coding question based on DP for 25 minutes and 30 MCQs on Java , OOPS and code snippet questions also some basic questions based on trees like number of leaf nodes in a complete binary tree with n nodes.

Q1. Write code for finding palindrome of a string
Ans. 
Code to find palindrome of a string
• Iterate through the string from both ends and compare characters

• Use two pointers, one starting from the beginning and one from the end

• If characters at both pointers match, continue checking until they meet in the middle

• If all characters match, the string is a palindrome
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Q2. What is dynamic memory allocation in Java
Ans. 
Dynamic memory allocation in Java refers to the process of allocating memory for objects at runtime.
• Dynamic memory allocation allows for objects to be created and destroyed during program execution.

• The 'new' keyword is used to dynamically allocate memory for objects in Java.

• Dynamic memory allocation helps in managing memory efficiently by allocating memory only when needed.

• Example: int[] arr = new int[5]; dynamically a
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Q3. You are designing an e commerce website which database will you choose and what will you use for authentication given that you can't use JWT or even third party like Google authentication
Ans. 
I would choose a relational database like MySQL and implement a custom authentication system using session management.
• Choose a relational database like MySQL for storing user data, product information, and orders.

• Implement a custom authentication system using session management to securely authenticate users without JWT or third-party services.

• Use encryption techniques to store and validate user passwords securely.

• Util...read more
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Q1. Find the character with the maximum frequency
Ans. 
Iterate through each character in the array of strings and keep track of the frequency of each character. Return the character with the maximum frequency.
• Create a dictionary to store the frequency of each character

• Iterate through each string in the array and then through each character in the string

• Update the frequency count of each character in the dictionary

• Return the character with the maximum frequency
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Q2. Valid parenthesis
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Q1. Have you used Junit? What is the difference between SQl and NoSQl Databases? have you worked with Kafka? Kafka based questions. explain dockerization/ containerization. which java8 feature did you work wit...read more
Ans. 
Yes, I have experience with Junit, SQL and NoSQL databases, Kafka, Dockerization, Java 8 features, stream() operations, and shell scripting in Unix.
• I have used Junit for unit testing in Java projects.

• SQL databases are relational databases that use structured query language for data manipulation, while NoSQL databases are non-relational databases that provide flexible schema design and horizontal scalability.

• I have work...read more
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Q1. What is the most complex sql query you have written till date. Why did you use nested query to achieve your goal? explain the query. which join did you use in the query. have you implemented hashset? how w...read more
Ans. 
The most complex SQL query involved nested queries for data manipulation. Used inner join. Implemented hashset and avoided trees due to their drawbacks.
• Nested SQL query used for complex data manipulation

• Inner join used for combining data from multiple tables

• Implemented hashset for efficient data storage and retrieval

• Avoided trees due to their drawbacks such as unbalanced structure and slower traversal times
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Q2. Find and replace words in a file using shell scripting. add an index in the beginning of each line in a file using shell scripting. what is multithreading? difference between single threaded and multithrea...read more
Ans. 
Shell scripting for find and replace, adding index to lines, multithreading, hashmap vs hashtable, stack vs queue
• Use sed command for find and replace in shell scripting

• Use awk command to add an index at the beginning of each line in a file

• Multithreading is the ability of a CPU to execute multiple threads concurrently

• Single threaded means only one thread is executed at a time, while multithreaded allows multiple threads...read more
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Q1. Behavioral questions- tell me about yourself. do you have any questions for us?
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Q1. Describe your work in current project
Ans. 
I am currently working on developing a web application for a client in the e-commerce industry.
• Developing front-end using React.js and back-end using Node.js

• Implementing payment gateway integration for seamless transactions

• Optimizing website performance for better user experience
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Q1. Describe the current design of the project
Ans. 
The current design of the project is a microservices architecture with a front-end built using React and a back-end using Node.js.
• Microservices architecture is used for scalability and flexibility

• Front-end is developed using React for a dynamic user interface

• Back-end is built with Node.js for server-side logic
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