100+ Principal Software Engineer Interview Questions and Answers

Calculate average, top 10 and bottom 10 elements of a given stream of integers.

• Create a variable to store the sum of integers and another variable to store the count of integers.

• Use a loop to read the integers from the stream and update the sum and count variables.

• Calculate the average by dividing the sum by the count.

• Sort the integers in ascending order and print the first 10 elements for bottom 10.

• Sort the integers in descending order and print the first 10 elements for top...read more

Static variables can be accessed from non-static methods using an object reference or by making the variable non-static.

• Static variables can be accessed from non-static methods by creating an object of the class containing the static variable.

• Alternatively, the static variable can be made non-static to be accessed directly from a non-static method.

• Attempting to access a static variable directly from a non-static method will result in a compilation error.

Implementation of Linked List with add, display, insert at end and delete operations.

• Create a Node class with data and next pointer

• Create a LinkedList class with head pointer

• Add method to add a new node at the end of the list

• Display method to print all nodes in the list

• Insert at end method to insert a new node at the end of the list

• Delete method to delete a node from the list

I have extensive experience designing scalable data-intensive applications, focusing on performance, reliability, and maintainability.

• Microservices Architecture: In a recent project, I designed a microservices architecture for a financial application, allowing independent scaling of services based on load.

• Database Sharding: Implemented sharding in a large-scale e-commerce platform to distribute data across multiple databases, improving query performance and reducing latency.

• C...read more

I am looking for change to explore new challenges and opportunities. Qualys offers a variety of work in cybersecurity and cloud security.

• Seeking new challenges and opportunities to grow professionally

• Interested in cybersecurity and cloud security

• Excited about the diverse range of projects at Qualys

Two objects created - one in the string pool and one in the heap.

• String 'a' is created in the string pool, while String 'b' is created in the heap.

• String pool is a special area in the heap memory where strings are stored to increase reusability and save memory.

• Using 'new' keyword always creates a new object in the heap, even if the content is the same as an existing string in the pool.

Only the original string 'Something' will be garbage collected.

• The concat method in Java does not modify the original string, but instead returns a new string with the concatenated value.

• In this case, 'a' remains as 'Something' and a new string 'Something New' is created, but not assigned to any variable.

• Since the new string is not stored in any variable, it will not be garbage collected.

Java 8 Date and Time API provides improved date and time handling capabilities.

• Introduction of new classes like LocalDate, LocalTime, LocalDateTime, ZonedDateTime, OffsetTime, OffsetDateTime, and Instant for better date and time manipulation

• Support for time zones and offsets

• Ability to perform date and time calculations easily

• Enhanced formatting and parsing capabilities

• Integration with existing date and time classes like java.util.Date and java.util.Calendar

Some strategies to improve Angular application performance

• Use lazy loading for modules to reduce initial load time

• Optimize change detection by using OnPush strategy

• Minimize the use of two-way data binding

• Implement server-side rendering for faster initial page load

• Use AOT (Ahead-of-Time) compilation to reduce bundle size

Arrays are used for ordered collections, HashSet for unique elements, and HashMap for key-value pairs.

• Use arrays when you need to store elements in a specific order and access them by index.

• Use HashSet when you need to store unique elements and do not care about the order.

• Use HashMap when you need to store key-value pairs and quickly retrieve values based on keys.

Merge and remove duplicates from two sorted arrays without using Collections

• Use two pointers to iterate through both arrays simultaneously

• Compare elements at each pointer and add the smaller one to the result array

• Skip duplicates by checking if the current element is equal to the previous element

Locking in distributed systems ensures data consistency and prevents conflicts during concurrent operations.

• Use distributed locks with tools like ZooKeeper or etcd to manage access to shared resources.

• Implement optimistic locking by using versioning to detect conflicts before committing changes.

• Consider using a consensus algorithm like Paxos or Raft to ensure agreement on the state of resources.

• Leverage database features like row-level locking or transactions to maintain cons...read more

Implement two stacks using a single array without extra space.

• Divide the array into two halves and use one half for each stack.

• Keep track of the top of each stack separately.

• Handle stack overflow and underflow conditions.

• Example: Implementing two stacks for undo and redo operations in a text editor.

I chose a different design approach based on specific project requirements and constraints.

• Considered project requirements and constraints when deciding on design approach

• Different designs may have different trade-offs and considerations

• Example: Chose a design that prioritized scalability over simplicity due to anticipated growth in user base

Design a scalable web crawler to efficiently index web pages and extract relevant data.

• Define the scope: Determine which websites to crawl and what data to extract (e.g., text, images).

• Use a distributed architecture: Implement multiple crawler instances to handle large-scale crawling.

• Implement a queue system: Use a message queue (like RabbitMQ) to manage URLs to be crawled.

• Respect robots.txt: Ensure the crawler adheres to the rules set by websites regarding crawling.

• Handle du...read more

Optimize page performance by reducing load times through various strategies like caching, lazy loading, and efficient queries.

• Implement caching strategies (e.g., Redis or Memcached) to store frequently accessed data.

• Use lazy loading for images and other resources to load them only when they are in the viewport.

• Optimize database queries by using indexing and avoiding N+1 query problems.

• Minimize HTTP requests by combining CSS and JavaScript files.

• Utilize Content Delivery Networ...read more

A movie booking app system design involves user authentication, movie selection, seat reservation, payment processing, and booking confirmation.

• User authentication: Implement login/signup functionality for users.

• Movie selection: Display list of movies with details like showtimes, ratings, and genres.

• Seat reservation: Allow users to select seats for chosen movie showtime.

• Payment processing: Integrate payment gateway for secure transactions.

• Booking confirmation: Send confirmati...read more

Joins and merges are used to combine data from multiple tables in SQL and Python.

• Joins in SQL are used to combine rows from two or more tables based on a related column between them.

• Types of joins in SQL include INNER JOIN, LEFT JOIN, RIGHT JOIN, and FULL JOIN.

• Merging in Python is done using the pandas library, where two DataFrames are combined based on a common column.

• Example: SQL - SELECT * FROM table1 INNER JOIN table2 ON table1.id = table2.id

• Example: Python - merged_df = ...read more

I handle critical application incidents by following a structured incident response process.

• Quickly assess the severity and impact of the incident

• Notify relevant stakeholders and form an incident response team

• Identify the root cause of the issue and implement a temporary fix if needed

• Communicate updates and progress to stakeholders regularly

• Conduct a post-incident review to learn from the incident and prevent future occurrences

Technical solutions are derived by analyzing the problem, researching existing solutions, brainstorming with team, prototyping, and testing.

• Analyze the problem statement thoroughly to understand the requirements and constraints.

• Research existing solutions and technologies to see if any can be leveraged or modified.

• Brainstorm with team members to gather different perspectives and ideas.

• Prototype the solution to quickly test and iterate on different approaches.

• Test the solution...read more

The interview process at Oracle typically involves multiple stages, including technical assessments and behavioral interviews.

• Initial screening: A recruiter reviews your resume and conducts a brief phone interview to assess your fit for the role.

• Technical interview: You may face coding challenges or system design questions, such as designing a scalable application.

• Behavioral interview: Expect questions about teamwork and conflict resolution, like describing a time you overcam...read more

The 'Volatile' keyword in C# is used to indicate that a field might be modified by multiple threads that are executing at the same time.

• Ensures that any read or write operation on the variable is done directly from the main memory and not from the CPU cache.

• Useful when working with multithreaded applications to prevent unexpected behavior due to caching.

• Example: 'volatile int count = 0;'

I ensure adherence to architectural design through structured processes, documentation, and regular reviews.

• Establish clear architectural guidelines and principles that align with business goals.

• Conduct regular design reviews to ensure compliance with architectural standards, such as using peer reviews in code development.

• Utilize architectural documentation tools like C4 model diagrams to visualize and communicate the architecture effectively.

• Implement automated testing and C...read more

I ensure architecture aligns with industry standards through continuous learning, collaboration, and leveraging best practices.

• Stay updated with industry trends by attending conferences and webinars, such as AWS re:Invent or Google I/O.

• Engage in code reviews and architectural discussions with peers to gather diverse perspectives and insights.

• Utilize established design patterns and frameworks, like Microservices or Event-Driven Architecture, to enhance scalability and maintain...read more

Oracle is a multinational computer technology corporation that specializes in developing and marketing database software and technology.

• Oracle is known for its flagship product, the Oracle Database, which is widely used in enterprise applications.

• It also offers a range of other software products, including middleware, application development tools, and cloud services.

• Oracle has a strong presence in the enterprise market and is a major competitor to other database vendors like...read more

Regression testing is the process of retesting modified software to ensure that previously working functionalities still work as expected.

• Regression testing is performed after making changes to software to identify any new defects or issues introduced.

• It helps ensure that existing functionalities are not affected by the changes made.

• Regression testing can be done manually or using automated testing tools.

• It involves re-executing test cases that cover the affected areas of the...read more

Emulate Producer/Consumer Problem using code

• Create a shared buffer between producer and consumer

• Use synchronization mechanisms like mutex or semaphore to control access to the buffer

• Implement producer and consumer functions to add and remove items from the buffer respectively