40+ Amazon Interview Questions and Answers

I participated in a coding challenge that tested JavaScript concepts like currying and object flattening.

• The coding challenge involved implementing a function that demonstrates currying in JavaScript.

• Another part of the challenge required flattening nested objects using recursion.

• I used higher-order functions and closures to achieve currying in the challenge.

• The challenge also tested my understanding of object manipulation and traversal in JavaScript.

Use a hashmap to store seen elements and check if complement exists in the hashmap.

• Create a hashmap to store seen elements.

• Iterate through the array and for each element, check if the complement (k - current element) exists in the hashmap.

• If complement exists, return the pair of integers.

• Example: For array [2, 7, 11, 15] and sum 9, the pair of integers is (2, 7).

Connect nodes of a tree on the same level

• Use a queue to traverse the tree level by level

• For each level, connect the nodes using their next pointer

• If a node has no next node, set its next pointer to null

useMemo is used to memoize a value, while useCallback is used to memoize a function.

• useMemo is used to optimize expensive calculations by caching the result.

• useCallback is used to optimize the rendering of child components by memoizing event handlers.

• useMemo returns the cached value, while useCallback returns the memoized function.

• Both hooks take a dependency array to determine when to recalculate or re-render.

Anagrams of a string are words or phrases formed by rearranging the letters of the original string.

• Create a hashmap to store the frequency of characters in the input string

• Iterate through the array of strings and check if the frequency of characters matches with the input string

• Add the strings that are anagrams of the input string to the result array

Low level design machine coding involves writing detailed code for specific functions or algorithms.

• Identify the specific functionality or algorithm to be implemented

• Break down the functionality into smaller components

• Write detailed code for each component, considering efficiency and optimization

• Test and debug the code to ensure it works as expected

Progress bar in React can be designed using CSS and state management.

• Use CSS to style the progress bar

• Use state management to update the progress value dynamically

• Consider using libraries like react-progress-bar to simplify implementation

Add two numbers represented as a linked list

• Traverse both linked lists and add corresponding nodes

• Handle carry over to next node

• Create a new linked list to store the result

useState is a hook in React that allows functional components to manage state.

• useState is a built-in hook in React.

• It allows functional components to have stateful logic.

• useState returns an array with two elements: the current state value and a function to update it.

• The initial state value is passed as an argument to useState.

• The state value can be of any data type, including objects and arrays.

• The update function returned by useState can be called to modify the state value.

• C...read more

useEffect is a React Hook used to perform side effects in functional components.

• useEffect is used to handle side effects like data fetching, subscriptions, or manually changing the DOM.

• It takes two arguments: a function that contains the side effect logic, and an optional array of dependencies.

• The function inside useEffect is executed after the component renders and after every update, unless dependencies are specified.

• If dependencies are provided, the effect will only be re-...read more

Design Uber supplier dispatch

• Create a system to match drivers with riders based on location and availability

• Use real-time data to optimize dispatching and reduce wait times

• Implement a rating system to ensure quality service from drivers

• Integrate with payment and mapping systems for seamless user experience

Implement tree traversal algorithm to visit each node in a tree structure

• Use depth-first search (DFS) or breadth-first search (BFS) to traverse the tree

• DFS can be implemented using recursion or a stack data structure

• BFS can be implemented using a queue data structure

• Example: Inorder traversal of a binary tree - left, root, right

An in-memory database is a database that primarily relies on main memory for data storage and retrieval.

• Utilize data structures like hash tables or trees for fast data access

• Implement caching mechanisms to optimize performance

• Consider data persistence strategies for durability

• Support for transactions and concurrency control

• Example: Redis, Memcached

Design a notification service for sending alerts to users.

• Use a scalable messaging system like Kafka or RabbitMQ to handle high volume of notifications.

• Implement a user subscription system to allow users to choose which notifications they want to receive.

• Include different channels for notifications such as email, SMS, and push notifications.

• Consider implementing a scheduling system to send notifications at specific times.

• Ensure notifications are personalized and relevant to e...read more

Splitwise is a bill splitting application where users can track and split expenses with friends.

• Design classes for User, Expense, Group, and Transaction

• Implement functions for adding expenses, settling debts, and generating reports

• Consider scalability and data storage options like databases

• Handle currency conversions and real-time updates for balances

I designed the HLD for our current project implementation.

• Identified the main components and their interactions

• Created a high-level architecture diagram

• Considered scalability, maintainability, and performance

• Collaborated with team members to ensure alignment with requirements

API testing is the process of testing APIs to ensure they meet functionality, reliability, performance, and security requirements.

• Ensures that APIs work as expected and meet specifications

• Verifies functionality, reliability, performance, and security of APIs

• Helps identify bugs, errors, and issues in the API

• Ensures compatibility with different systems and environments

• Automates testing processes for efficiency

• Examples: testing API endpoints, data validation, error handling

In React JS, timers can be implemented using setInterval or setTimeout functions.

• Use setInterval for recurring timers

• Use setTimeout for one-time timers

• Remember to clear the timer using clearInterval or clearTimeout when component unmounts

Find the path in a matrix with the longest sum of elements

• Start from the top-left corner of the matrix

• Move only right or down in the matrix

• Keep track of the sum of elements in each path

• Return the path with the longest sum

Left view of a binary tree is the set of nodes visible when the tree is viewed from the left side.

• The leftmost node at each level is included in the left view.

• Use depth-first search to traverse the tree and keep track of the maximum level seen so far.

• If the current node is at a level greater than the maximum level seen so far, add it to the left view and update the maximum level seen.

Sliding window negative numbers in window

• Implement a sliding window algorithm to find the maximum sum of a subarray of size k

• Use a double-ended queue (deque) to efficiently maintain the maximum element in the window

• Handle negative numbers by checking if the maximum element is outside the current window

The right view of a binary tree shows the rightmost node at each level.

• Traverse the tree in a depth-first manner, starting from the right child of each node.

• Keep track of the current level and only add the rightmost node of each level to the result.

• Example: For the tree [1,2,3,null,5,null,4], the right view is [1,3,4].

Hybrid mode refers to a combination of remote and in-office work, common in early stage startups.

• Hybrid mode allows for flexibility in work location, combining the benefits of remote work with in-person collaboration.

• Working in early stage startups can be exciting and fast-paced, with opportunities to take on diverse responsibilities and make a significant impact.

• It is important to be adaptable and willing to wear multiple hats in a startup environment.

• Communication skills ar...read more

I approach designing for a problem statement by conducting research, brainstorming ideas, creating prototypes, and testing solutions.

• Start by thoroughly understanding the problem statement and the needs of the users

• Conduct research to gather insights and data related to the problem

• Brainstorm potential solutions and sketch out initial concepts

• Create prototypes to visualize and test different design ideas

• Iterate on the prototypes based on feedback and user testing

• Finalize the d...read more

Detect loop in linkedlist and iterative preorder traversal of binary tree

• To detect a loop in a linked list, we can use Floyd's Cycle Detection Algorithm by using two pointers - slow and fast.

• For iterative preorder traversal of a binary tree, we can use a stack to keep track of nodes and visit them in the correct order.

• Example: For detecting a loop in a linked list, if the slow and fast pointers meet at some point, then there is a loop.

• Example: For iterative preorder traversal...read more

Count the number of 2s in a given number

• Iterate through each digit of the number and count the occurrences of 2

• Convert the number to a string for easier manipulation

• Handle edge cases like negative numbers or zero

I prioritize tasks based on urgency and importance, communicate with stakeholders for realistic deadlines, and delegate when necessary.

• Prioritize tasks based on urgency and importance

• Communicate with stakeholders for realistic deadlines

• Delegate tasks when necessary

Approximately 3 million vehicles are estimated to be running in Mumbai at any given time.

• Consider the total number of registered vehicles in Mumbai

• Factor in the percentage of vehicles that are typically on the road during peak hours

• Take into account the different types of vehicles such as cars, bikes, buses, and trucks

• Consider the traffic congestion levels in different areas of Mumbai

The Hotel management system is a software solution that helps in managing various operations of a hotel.

• The system should have modules for managing reservations, check-ins, check-outs, and room availability.

• It should allow the hotel staff to assign rooms to guests and manage room rates.

• The system should handle billing and payment processing.

• It should provide reporting and analytics features to track hotel performance.

• Integration with other systems like online booking platform...read more

Vertical Order Traversal of a tree

• Vertical order traversal is a way to traverse a binary tree from top to bottom, left to right

• Nodes are printed in order of their horizontal distance from the root node

• If two nodes have the same horizontal distance, they are printed in the order they appear in the tree

A user-friendly digital app for convenient online food ordering with various restaurant options and customizable orders.

• User-friendly interface for easy navigation

• Integration with multiple restaurants for a wide variety of options

• Customizable orders with options for special requests

• Secure payment gateway for seamless transactions

• Order tracking feature for real-time updates

Parking lot design involves layout, size, capacity, and efficiency considerations.

• Consider the layout to maximize space and ease of access for vehicles.

• Include designated spots for different types of vehicles (e.g. compact, electric, disabled).

• Implement efficient traffic flow patterns to reduce congestion and improve safety.

• Incorporate technology like sensors and automated payment systems for convenience.

• Ensure proper lighting and security measures for safety of vehicles and ...read more

BDD (Behavior Driven Development) framework is a software development approach that focuses on collaboration between developers, QA, and non-technical stakeholders.

• BDD involves writing scenarios in plain language using Gherkin syntax (Given, When, Then)

• Scenarios are written from the perspective of an end user's behavior

• BDD helps in improving communication and understanding between team members

• Popular BDD frameworks include Cucumber, SpecFlow, and Behave

Low level design of Twitter involves various components like servers, databases, APIs, and algorithms.

• Twitter uses a distributed system architecture with multiple servers for handling user requests and data storage.

• The system uses a combination of relational and NoSQL databases for storing user data and tweets.

• APIs are used for communication between different components of the system and for providing access to third-party developers.

• Twitter uses various algorithms for tasks ...read more

ES6 updates refer to the new features and syntax improvements introduced in ECMAScript 6, also known as ES2015.

• Arrow functions for more concise syntax

• Let and const for block-scoped variables

• Classes for object-oriented programming

• Template literals for easier string interpolation

• Destructuring assignment for extracting values from arrays and objects

• Spread and rest operators for easier manipulation of arrays and objects

Design a system for booking airplane tickets efficiently and securely.

• Create a user-friendly interface for customers to search and book flights.

• Implement a secure payment system for processing transactions.

• Include features for managing flight schedules, seat availability, and pricing.

• Integrate with airlines' reservation systems for real-time updates.

• Provide options for seat selection, meal preferences, and special requests.

• Generate e-tickets and send confirmation emails to cu...read more

Current system is a web-based application for managing customer data and orders.

• Frontend built with React for user interface

• Backend built with Node.js and Express for server-side logic

• Database using MySQL for storing customer data and orders

• Authentication using JWT tokens for secure access

Arrow functions are concise and have implicit return, while normal functions have more flexibility and can be named.

• Arrow functions are written with a concise syntax using '=>'

• Arrow functions do not have their own 'this' keyword

• Normal functions can be named and have more flexibility in terms of syntax and behavior

File upload progress can be tracked using various methods.

• Use AJAX to send progress updates to the server

• Use HTML5 File API to track progress on the client side

• Use server-side libraries like multer to track progress on the server side

Manual testing process involves executing test cases manually without the use of automation tools.

• Creating test cases based on requirements

• Executing test cases manually

• Recording test results

• Reporting defects

• Re-testing fixed defects

AP and AR cycle refers to the process of accounts payable and accounts receivable in a company.

• AP cycle involves receiving and processing invoices from vendors, making payments, and maintaining accurate records.

• AR cycle involves sending invoices to customers, receiving payments, and reconciling accounts.

• Efficient AP and AR cycles are crucial for maintaining healthy cash flow and relationships with vendors and customers.

Use sorting or heap data structure to find top k elements in an array.

• Sort the array in descending order and return the first k elements.

• Use a max heap data structure to efficiently find the top k elements.

• Time complexity can be O(n log n) for sorting or O(n log k) for heap method.

Event loop is a mechanism in JavaScript that allows for asynchronous operations to be executed in a non-blocking way.

• Event loop continuously checks the call stack for any functions that need to be executed.

• If the call stack is empty, the event loop checks the callback queue for any pending tasks.

• Event loop moves tasks from the callback queue to the call stack for execution.

• Example: setTimeout function in JavaScript uses event loop to execute a function after a specified delay...read more

Extract numbers from a string and return as an array of strings.

• Use regular expressions to match digits in the string.

• Iterate through the string and extract digits using isdigit() function.

• Split the string using non-digit characters as delimiters and return the resulting array.

The problem involves finding the sum of all possible subarrays in an array of integers.

• Use nested loops to iterate through all possible subarrays

• Keep track of the sum of each subarray as you iterate

• Consider edge cases like empty array or negative numbers

Experience working with REST API's in previous roles.

• Developed and maintained RESTful APIs for various applications

• Used tools like Postman for testing and debugging API endpoints

• Worked with JSON and XML data formats for API communication

Common tools for troubleshooting include log analysis tools, network monitoring tools, and remote desktop tools.

• Log analysis tools such as Splunk or ELK stack can help identify errors and issues in application logs.

• Network monitoring tools like Wireshark or Nagios can help pinpoint network-related problems.

• Remote desktop tools like TeamViewer or AnyDesk can be used to troubleshoot issues on end-user machines remotely.

I have experience using Splunk for log management and analysis.

• Utilized Splunk to monitor and analyze log data for troubleshooting issues

• Created custom dashboards and alerts to track system performance

• Used Splunk queries to identify patterns and trends in log data

• Integrated Splunk with other tools for seamless data analysis