Infosystems Web Developer Interview Questions and Answers

Round duration - 60 Minutes
Round difficulty - Easy

Q1. 
0/1 Knapsack Problem Statement
A thief is planning to rob a store and can carry a maximum weight of 'W' in his knapsack. The store contains 'N' items where the ith item has a weight of 'wi' and a value of...read more
Ans. 
Yes, the 0/1 Knapsack problem can be solved using dynamic programming with a space complexity of not more than O(W).
• Use a 1D array to store the maximum value that can be stolen for each weight capacity from 0 to W.

• Iterate through each item and update the array based on whether including the item would increase the total value.

• The final value in the array at index W will be the maximum value that can be stolen.
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Q2. 
Find the Second Largest Element
Given an array or list of integers 'ARR', identify the second largest element in 'ARR'.
If a second largest element does not exist, return -1.
Example:
Input:
ARR = [2,...read more
Ans. 
Find the second largest element in an array of integers.
• Iterate through the array to find the largest and second largest elements.

• Handle cases where all elements are identical.

• Return -1 if a second largest element does not exist.
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Round duration - 60 Minutes
Round difficulty - Easy

System Design Round

Q1. Design a system for Twitter, discussing its architecture, key components, and scalability considerations.
Ans. 
Design a scalable system for Twitter with key components and architecture.
• Use microservices architecture for scalability and fault isolation.

• Key components include user service, tweet service, timeline service, and notification service.

• Use a distributed database like Cassandra for storing tweets and user data.

• Implement a message queue like Kafka for handling real-time updates and notifications.

• Use a caching layer like ...read more
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Round duration - 30 Minutes
Round difficulty - Easy

It is just a formality

Q1. General discussion on experience
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Q1. Knowledge on SQL and how to write a query
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Q2. Knowledge on DSA and coding problems to solve.
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Q3. Knowledge on APIS (structure, security etc.)
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Q1. Difference between Procedure, Packages and functions.
Ans. 
Procedures, Packages and Functions are all subprograms in PL/SQL with different characteristics.
• Procedures are subprograms that perform a specific task and may or may not return a value.

• Functions are subprograms that always return a value and can be used in SQL statements.

• Packages are a collection of related procedures, functions, variables, and other program constructs that can be used as a single unit.

• Packages provid...read more
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Q2. If table or view does not exist what does it mean
Ans. 
It means that the table or view does not exist in the database.
• The query will fail and return an error message.

• The application may crash or behave unexpectedly.

• The table or view may have been deleted or renamed.

• Check the spelling and syntax of the query.

• Make sure the database connection is established and valid.
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Q3. Difference Between Views and Materialized Views
Ans. 
Views are virtual tables while Materialized Views are physical tables.
• Views are created using SELECT statement while Materialized Views are created using CREATE MATERIALIZED VIEW statement.

• Views do not store data while Materialized Views store data.

• Views are updated dynamically while Materialized Views are updated manually or automatically based on refresh settings.

• Materialized Views are faster for read-heavy workloads...read more
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Q1. Details explanation about the projects and the concepts what we used.
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Q1. Explain dependency injection, indexes in sql, SOLID principles.
Ans. 
Dependency injection is a design pattern where dependencies are injected into a class rather than created within the class itself.
• Dependency injection helps in achieving loose coupling between classes.

• It allows for easier testing and maintenance of code.

• Example: Constructor injection, setter injection, and interface injection are common types of dependency injection.

• Indexes in SQL are used to improve the performance of...read more
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Q1. Sql injection and how to prevent
Ans. 
SQL injection is a type of attack where malicious SQL statements are inserted into an entry field for execution.
• Use parameterized queries or prepared statements

• Sanitize user input by validating and escaping special characters

• Limit database user privileges

• Use a web application firewall

• Regularly update and patch software
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Q1. How to optimize websites
Ans. 
Optimizing websites involves improving speed, user experience, and search engine ranking.
• Minimize HTTP requests

• Optimize images and videos

• Use caching and compression

• Reduce server response time

• Implement lazy loading

• Use a content delivery network (CDN)

• Optimize code and scripts

• Ensure mobile responsiveness

• Improve website security

• Use structured data for SEO
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Q1. What is the interceptor
Ans. 
An interceptor is a software component that intercepts and modifies the behavior of a program or system.
• Interceptors are commonly used in software frameworks to add additional functionality to an application.

• They can be used to intercept and modify incoming or outgoing requests, such as adding authentication or logging.

• Interceptors can also be used to intercept method calls and perform actions before or after the metho...read more
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What is model binding

Q1. What is design pattern
Ans. 
Design pattern is a reusable solution to a commonly occurring problem in software design.
• Design patterns help in creating maintainable, scalable, and reusable code.

• They provide a common language for developers to communicate about solutions.

• Examples include Singleton, Factory, Observer, and Strategy patterns.
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I was asked with writing the code and algorithms. Also lots of MySQL queries