Avalara Technologies Senior Engineer Interview Questions and Answers

Normal online code / frontend test

Q1. How would you build book my show
Ans. 
Designing and building a platform similar to BookMyShow involves creating a user-friendly interface for booking tickets for various events.
• Develop a user-friendly website and mobile app for users to browse and book tickets for movies, concerts, plays, etc.

• Implement a secure payment gateway for users to make online transactions.

• Integrate a database to store information about events, venues, tickets, and user bookings.

• In...read more
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Q1. Solid principals, awareness of patterns
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Q1. How would you build tinyurl like service, systems designs
Ans. 
To build a tinyurl-like service, design a system with a URL shortening algorithm, a database to store mappings, and a redirect service.
• Use a hashing algorithm to generate short URLs from long URLs (e.g. MD5, SHA-256).

• Store the mappings of short URLs to long URLs in a database (e.g. MySQL, Redis).

• Implement a redirect service that takes a short URL, looks up the corresponding long URL in the database, and redirects the u...read more
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Q1. Non-technical questions
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Q1. Find longest palindromic substring in a given string.
Ans. 
Use dynamic programming to find the longest palindromic substring in a given string.
• Iterate through the string and expand around each character to find palindromes.

• Store the length of the longest palindrome found so far.

• Return the substring based on the start and end indices of the longest palindrome.
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Q2. How to serialize and deserialise a tree
Ans. 
To serialize and deserialize a tree, use a recursive approach to traverse the tree and store the data in a suitable format.
• Use pre-order traversal to serialize the tree by storing the node values in a list or string.

• For deserialization, reconstruct the tree by recursively building nodes from the serialized data.

• Consider using JSON or XML format for serialization to easily store and retrieve tree structure.
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Q3. Find if a given regex (containing ., * and lower case english chars) matches a given string.
Ans. 
Use regex library to match given regex with string.
• Use a regex library like re in Python to match the given regex with the string.

• Check if the regex matches the string using the library functions.

• Handle cases where the regex contains special characters like . and * appropriately.
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Q4. Explain about throttling and implement throttle function.
Ans. 
Throttling is a technique used to control the rate of requests sent to a server.
• Throttling helps prevent server overload by limiting the number of requests processed at a time.

• Implementing a throttle function involves setting a maximum request rate and delaying excess requests.

• Example: Implementing a throttle function in a web application to limit the number of API calls made to a third-party service.

• Example: Throttlin...read more
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Q1. Find squares of elements in a sorted array and return the sorted response.
Ans. 
Sort the squares of elements in a sorted array and return the sorted response.
• Iterate through the array and square each element.

• Store the squared values in a new array.

• Sort the new array and return it.
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Q2. Write a short promise example and implement your own promise
Ans. 
A promise is a commitment to do something in the future, typically used for asynchronous operations in JavaScript.
• Promises are used to handle asynchronous operations in JavaScript.

• They represent a value that may be available now, in the future, or never.

• Promises have three states: pending, fulfilled, or rejected.

• Example: new Promise((resolve, reject) => { setTimeout(() => resolve('Done!'), 1000); });
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Q3. Explain event loop, what are different types of queues in event loop
Ans. 
Event loop is a mechanism that allows for asynchronous execution of code by managing the order of events in a single thread.
• Event loop continuously checks the call stack for any functions that need to be executed, and processes them in a non-blocking manner.

• Different types of queues in event loop include microtask queue (Promise callbacks), macrotask queue (setTimeout, setInterval callbacks), and animation frame queue
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Q4. What is virtual DOM and why its faster
Ans. 
Virtual DOM is a lightweight copy of the actual DOM, used to improve performance by minimizing direct manipulation of the real DOM.
• Virtual DOM is a concept used in frameworks like React to optimize rendering performance.

• Changes are first made to the virtual DOM, which is then compared to the real DOM to identify the minimal updates needed.

• This approach reduces the number of actual DOM manipulations, resulting in faster...read more
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Q1. Why do we use SOLID principle, SRP and OCP violation?
Ans. 
SOLID principles help in creating maintainable, scalable, and flexible software.
• SOLID principles help in creating software that is easier to maintain and extend.

• Single Responsibility Principle (SRP) ensures that a class has only one reason to change, leading to more modular and cohesive code.

• Open/Closed Principle (OCP) states that a class should be open for extension but closed for modification, allowing for easy chang...read more
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Q2. What is singleton design pattern and how to implement it?
Ans. 
Singleton design pattern ensures a class has only one instance and provides a global point of access to it.
• Create a private static instance of the class within the class itself.

• Provide a public static method to access the instance.

• Ensure the constructor of the class is private to prevent instantiation from outside the class.

• Example: Singleton pattern is commonly used in database connections to ensure only one connectio
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Q3. OOPs based question: abstract vs interface, multiple inheritance, method overloading vs method overriding.
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Q4. Dependency injection- what is it and any use case where to use?
Ans. 
Dependency injection is a design pattern where components are provided with their dependencies rather than creating them internally.
• Dependency injection helps in achieving loose coupling between components.

• It makes components easier to test by allowing for easier mocking of dependencies.

• Use cases include injecting database connections, logging services, and external API clients into components.
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Q1. Multithreading and TPL related questions?
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Q2. How can we debug the any published dll?
Ans. 
Debugging a published dll involves using tools like Visual Studio debugger and logging mechanisms.
• Use Visual Studio debugger to attach to the process using the published dll

• Set breakpoints in the code to pause execution and inspect variables

• Use logging mechanisms to track the flow of execution and identify issues

• Check for any exceptions or errors thrown by the dll
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Q3. Data seeding in entity framework and how to map tables with entity?
Ans. 
Data seeding in Entity Framework involves pre-populating database tables with initial data. Mapping tables with entities involves defining relationships between database tables and entity classes.
• Data seeding in Entity Framework can be done using the 'Seed' method in the 'Configuration' class of the DbContext.

• To map tables with entities, use data annotations or Fluent API to define relationships between entities and da...read more
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Q4. Deployment related question in IIS.
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Q1. Salary negotiation related discussion
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Q1. Basic java fundamentals
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Q2. Spring boot,sql
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Q1. Some technical questions from manager
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Q2. Some challenges or scenario based questions
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Q1. Salary discussion mostly
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Q2. Benifts that they offer with TR
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Q1. What is the importance of manual testing when compared to automation testing
Ans. 
Manual testing is important for exploratory testing, usability testing, and ad-hoc testing.
• Manual testing allows for exploratory testing where testers can explore the application and identify unexpected issues.

• Usability testing, which involves real users interacting with the software, is best done manually to capture user experience.

• Ad-hoc testing, where testers randomly test the application without predefined test cas...read more
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Q2. Real life scenario on web application testing
Ans. 
Testing a web application for an online shopping platform
• Testing the functionality of adding items to the cart and checking out

• Testing the payment gateway integration for secure transactions

• Testing the search functionality to ensure accurate results are displayed

• Testing the responsiveness of the website on different devices and browsers
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3 questions were there

Q1. Basic questions
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Q2. Os, dbms, core concept of cs
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Q1. Core concept of cs
Ans. 
Core concept of computer science is the study of algorithms and data structures.
• Algorithms are step-by-step procedures for solving problems.

• Data structures are ways to organize and store data efficiently.

• Examples include sorting algorithms like bubble sort and data structures like arrays and linked lists.
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