Tech/Behavioral Interview Questions SWE

What is Indexing in sql mysql?

Indexing is a technique in SQL/MySQL that speeds up data retrieval by creating a structured lookup, reducing the need for full table scans. It works like a book index, allowing the database to find data faster.

⭐️ Situation & Task:
In my Program Evaluation System project, we needed to store and retrieve large amounts of course evaluations, degrees, and instructor data efficiently. Without optimization, queries were slow when searching for evaluations by course or instructor.

⚙ Action:
I created indexes on degreeID, courseID, and instructorID to speed up queries. For example, I indexed courseID in the Course_Evaluation table to make retrieving course-specific evaluations much faster.

🏆 Result:
After adding indexes, query execution time significantly decreased, improving performance when retrieving student evaluation reports.

Q: Explain the difference between an array and a linked list.

A: An array stores elements in contiguous memory locations and provides constant-time access to elements using an index, but its size is fixed. A linked list stores elements in non-contiguous memory locations, with each node pointing to the next, allowing for dynamic resizing but requiring sequential access, which is slower for element lookup.

What is react

React is a JavaScript library that makes building websites easier by using components—small, reusable pieces of a webpage. It helps create fast and interactive user interfaces by only updating the parts of the page that change, instead of reloading everything. React also has hooks to manage data inside components and works great for single-page applications (SPAs) where the content updates without needing a full refresh.

What is left join in sql?

Returns all records from the left table and matching records from the right.

What is inheritance, and how does it relate to polymorphism in object-oriented programming?

A: Inheritance allows a class (child) to acquire properties and methods from another class (parent), promoting code reuse and hierarchy. Polymorphism builds on inheritance by enabling a child class to override parent methods, allowing different objects to respond differently to the same method call, enhancing flexibility and extensibility.

What are constraints in SQL, and can you provide examples of how you've used them?

Answer:
Constraints are rules enforced on data in a table to ensure accuracy and integrity. Common types of constraints include:

• PRIMARY KEY: Ensures each record is unique and not null.

• FOREIGN KEY: Maintains referential integrity between two tables.

• UNIQUE: Prevents duplicate values in a column.

• CHECK: Enforces a condition for the values in a column.

• NOT NULL: Ensures that a column cannot have a null value

Q: What’s the difference between overriding and overloading?

A: Overriding happens in inheritance when a child class changes a method from the parent class. Occurs during run time to pick what method will be called.When a system has different types of actions (e.g., payments) that share a base logic but require unique processing. Overloading happens in the same class when multiple methods have the same name but different parameters. Occurs at compile-time.

What is Node.js?

Handles API requests, database queries, and business logic.

Handles multiple requests asynchronously – Great for APIs & real-time applications.
✅ Uses JavaScript for both frontend & backend – No need to switch languages.

Explain the four principles of OOP

The four principles of object-oriented programming (OOP) are:

1. Encapsulation: is the practice of hiding an object's internal details like attributes and only allowing access through public methods, protecting data from unintended modification, ensuring data integrity.

2. Inheritance: Allowing one class (child) to inherit attributes and behaviors from another class (parent), promoting code reuse and hierarchical organization.

3. Polymorphism: Enabling methods to perform different tasks based on the context, such as method overloading or overriding, to improve flexibility and scalability.

4. Abstraction: Hiding complex implementation details and exposing only the essential features to simplify usage and reduce complexity.

Q: What is unit testing, and why is it important in software development?

A: Unit testing involves testing individual components or functions of a program to ensure they work correctly. It is important because it helps identify bugs early, ensures code reliability, and makes it easier to refactor or update code without breaking existing functionality.

What is dependency injection?

Dependency Injection (DI) is a design pattern used in object-oriented programming to manage dependencies between objects. Instead of a class creating its own dependencies, they are provided (injected) externally, making the code more modular, testable, and maintainable.Helps in building scalable backend applications where dependencies (like databases, logging, and APIs) are injected dynamically.

Explain compiled vs interpreted languages?

Compiled languages are converted directly into machine code by a compiler before execution, making them faster and more efficient at runtime (e.g., C++ or Java). Interpreted languages, on the other hand, are executed line-by-line by an interpreter, which makes them more flexible but generally slower (e.g., Python or JavaScript). Compiled languages require a build step, while interpreted languages are executed directly from the source code.

What does volatile keyword mean in C++?

The volatile keyword in C++ is used to indicate that a variable’s value can be changed unexpectedly, such as by hardware or another thread, and prevents the compiler from optimizing the code involving that variable. It ensures the program always fetches the variable’s value directly from memory rather than relying on a cached version, maintaining accuracy in scenarios like interacting with hardware registers or shared memory in multithreaded programs.

What is OOP in your own words?

Object-Oriented Programming (OOP) is a programming approach that organizes code into objects, which are instances of classes that contain both attributes and methods.It follows four key principles—encapsulation, inheritance, polymorphism, and abstraction—to make code more modular, reusable, and easier to maintain.

Q: Tell me about yourself.

I’m a software engineer with experience building full-stack and backend systems in Agile development environments. I’ve worked extensively with Git-based workflows, CI/CD pipelines, and REST APIs while developing and maintaining production applications. My core programming background is in C++, Java, Python, and PHP, and I’m comfortable adapting to new technologies quickly when needed, I love problem solving and buidling scable large scale system that are client centirc and bring the business value

Q: Tell me about a time where you made a mistake. How did you deal with the mistake, and what did you learn from it?

Situation:

During the TI E2E AI project, I initially built the scraper using synchronous requests, which worked but became very slow when scaling to large datasets.

Action:

After noticing the performance issue, I took ownership of improving it by refactoring the scraper to use asynchronous requests with aiohttp, allowing multiple pages to be fetched concurrently. I tested and validated the changes to ensure stability while significantly improving speed.

Result:

The scraper became much faster and more scalable, enabling us to process large volumes of data efficiently. I learned the importance of considering performance and scalability early, especially when working with large datasets.

Q: Describe a time your team encountered an issue during a project. How did you work together to overcome it?

S/T: For my PrimefocusDetailing website, we discovered it wasn’t displaying properly on mobile devices, which was critical since most customers accessed it through their phones.
A: My partner and I identified the issue by testing the site on mobile devices and analyzing the layout. Using CSS media queries, we adjusted button placements and screen sizing to fit smaller devices, while documenting the process to avoid similar issues in the future.
R: The mobile experience improved significantly, leading to positive customer feedback and higher conversions from mobile users compared to before.

Where do you see yourself in 5 or ten years?

In five years, I see myself as a highly skilled software engineer, continuously improving my expertise in software development, system architecture, and problem-solving. I aim to take on challenging projects, contribute to innovative solutions, and collaborate with cross-functional teams to build impactful software. In ten years, I hope to step into a senior or leadership role, mentoring junior engineers, leading technical projects, and shaping the development of cutting-edge technologies. My goal is to grow both technically and professionally, making meaningful contributions to my team and the company.

How do you ensure the quality and scalability of your code?

I follow best practices such as writing clean, modular code and conducting thorough code reviews. I rely on version control with Git/GitHub and use automated testing where possible. For instance, in my internship, I developed a Dockerized system that ensured consistency across environments and scalability under increased load. This process not only improves code quality but also minimizes potential deployment issues.

Describe a time when you had to collaborate with a team to complete a project under a tight deadline

Situation:

During our TI E2E AI project, our team had a tight deadline to deliver a working prototype that could scrape TI forum data and power an AI-driven knowledge retrieval system for our sponsor.

Action:

I collaborated closely with my teammates by taking ownership of the scraping pipeline, n8n workflow automation, and integrating embeddings into Qdrant, while regularly syncing to align with others working on the database and infrastructure. We divided responsibilities clearly, communicated frequently, and adjusted quickly when integration issues came up.

Result:

We successfully delivered a fully functional system on time that scraped thousands of posts, stored them as vector embeddings, and enabled fast, relevant AI-powered search—meeting our sponsor’s expectations and demonstrating real business value.

What is an API?

An API, or Application Programming Interface, is a way for different software systems to communicate by sending requests and receiving responses. It acts as a bridge that allows one system to use the functionality or data of another without needing to understand its internal implementation.

In my TI E2E AI project, I used FastAPI to create backend endpoints that allowed n8n to trigger the scraping process and send data for processing and storage in Qdrant, enabling seamless communication between all parts of the system.

Name a time you had to work with a difficult team member and how did you navigate that?

Situation/Task: In my project management class, my team of four was tasked with designing a fitness app that would recommend personalized training programs, diets, and nutrient plans for specific clients. We focused on creating a Statement of Work (SOW), defining key deliverables, and managing risks. However, one team member resisted collaboration, often dismissing others’ ideas and insisting on their own approach, which delayed progress.

Action: I initiated a one-on-one conversation to understand their concerns and emphasized the importance of teamwork to meet our project goals. I proposed structured brainstorming sessions and assigned clear roles to ensure everyone’s ideas were heard and aligned with the SOW and deliverables.

Result: The team member became more cooperative, and we successfully developed a detailed plan for the app, including key deliverables and risk mitigation strategies. This experience enhanced my conflict resolution and leadership skills while ensuring the project met its objectives.

Tell me a time you used OOP?

For a search engine project, I needed to design a system to efficiently retrieve keywords from over 300,000 financial news articles while maintaining fast and accurate access.

Action:

I applied object-oriented principles by designing separate classes for keyword indexing, document storage, and search functionality. I used encapsulation to keep data and methods organized within each class, and abstraction to expose only the necessary interfaces for searching and inserting data. Internally, I implemented a map with an AVL tree structure to ensure efficient operations while keeping the design modular and maintainable.

Result:

This approach improved both performance and code organization, and the project ranked in the top 3% of the class for speed and accuracy, demonstrating my ability to apply OOP to build scalable systems.

What’s your experience with SQL and MySQL?

Situation:
At Paycom, I regularly worked with MySQL while supporting backend services and resolving production issues.

Action:
I wrote and optimized SQL queries to retrieve and update data, especially when debugging issues or validating data across different parts of the system. I also ensured queries were efficient by focusing on proper filtering, joins, and only selecting necessary data to reduce load.

Result:
This helped me quickly diagnose and resolve issues while maintaining reliable and performant backend operations.

What would you do if one person on your team wasn’t pulling their weight?

Situation/Task: If a team member wasn’t contributing effectively, my goal would be to address the situation constructively to ensure the team’s success.

Action: I would start by having a private conversation to understand if they are facing challenges, such as workload issues or unclear expectations. I’d offer support, clarify their responsibilities, and suggest breaking tasks into manageable steps. If the issue persists, I’d communicate the situation to the team or project lead while focusing on solutions, not blame.

Result: This approach helps the team member re-engage while maintaining team morale and ensuring the project stays on track. It also demonstrates leadership by fostering collaboration and accountability.

What is your strongest weakness?

One weakness I've worked on is that I sometimes say yes to too many things because I like being dependable and helping wherever I can. Early on, I would take on additional tasks without always considering how they fit into my overall priorities. Over time, especially in professional environments like Paycom, I've learned to communicate priorities better and make sure I'm focusing on the highest-impact work first while still being a strong team contributor.”

Questions to ask after interview ?

1. If im selected for this role One Year from now how would you know that you made the right decision on me?

2. What does success look like for someone in this role within the first six months?

3. What are some challenges that someone in this position might face early on?

4. You are going to interview alot of people who can do the job but in your opinion what does the high performer look like?

5. After questions: Thank you, that was really helpful. Based on our conversation, the role sounds like a great fit for my experience and the type of engineering work I enjoy, so I’d definitely be excited to move forward in the process.

How would you define a good vs. great programmer?

A good programmer writes clean, efficient, and functional code while solving problems effectively and meeting deadlines. They understand the fundamentals, follow best practices, and collaborate well with their team.

A great programmer goes beyond that—they write scalable, maintainable code and think about long-term impacts. They proactively seek innovative solutions, mentor others, and anticipate challenges before they arise. A great programmer also communicates complex ideas clearly and contributes to improving the overall development process

What's the difference between an abstract class and an interface?

An interface only has pure virtual functions that must be implemented by a derived class.

An abstract class can have both pure virtual functions (abstract methods) and concrete methods that already have an implementation.

This means an interface is just a contract, while an abstract class can provide default behavior that derived classes can use. 🚀

Consider the top 3 programming languages that you are most familiar with. What would you choose, if you could add a feature from one of them to the other two?

My top 3 programming languages are C++, Python, and SQL.

If I could add a feature from one language to the other two, I would bring Python’s simplicity and dynamic typing to C++ and SQL.

• For C++, adding Python’s easy syntax and dynamic typing would simplify development and make rapid prototyping much faster.

• For SQL, integrating Python-like scripting would make writing complex queries and data manipulation more intuitive,

What is a RESTful API?

A REST API is a way for a client and server to communicate over HTTP using standard methods like GET, POST, PUT, and DELETE to access or modify resources, usually exchanging data in JSON format.

Give an example of inheritance?

Imagine you're building a financial software system for managing different types of transactions. You could have a base class called Transaction that contains shared properties and methods, such as the transaction amount, date, and a method to process the transaction. From this base, you could create specialized child classes that inherit from Transaction but add their own unique behavior. For example, a BankTransfer class could inherit the basic transaction structure but include additional attributes like a bank account number.A CreditCardPayment class would also inherit from Transaction but add properties such as a card number.

Why Did You Leave Paycom? Why Are You Looking for a New Role?

Paycom recently underwent organizational restructuring and consolidation across several roles, and my role was affected as part of that change. It gave me an opportunity to step back and look for my next role where I can continue growing as a software engineer and work on large-scale systems.

Tell Me About a Project You Led”

Situation

On the Position Management team at Paycom, clients wanted the ability to add reusable question templates to job postings, which the existing system didn’t support.

Action

The product team provided a general description and client feedback, and I translated those requirements into a full-stack solution. I designed how question templates would integrate with existing position and job posting data, coordinated with other modules to ensure compatibility, and implemented both backend logic and frontend functionality.

Result

The feature allowed users to attach reusable question templates to job postings, improving the workflow for hiring managers and addressing a common client request.

What Technologies Do You Work With at Paycom?

My primary languages are C++, Java, Python, and PHP. At Paycom I worked in a full-stack environment where I implemented backend logic, handled API interactions, and worked with frontend components as part of larger features in a Agile enviroment. I also regularly used Git for version control, participated in code reviews, and worked within CI/CD pipelines where automated tests had to pass before code was integrated.

Tell Me About a Time You Had to Learn Something Quickly

“During my Texas Instruments project, I had to learn Python very quickly because the project’s backend and scraping pipeline were built around Python technologies. Most of my prior experience was in Java and C++, so at first it was a challenge.

However, I already understood core programming and object-oriented concepts, so I focused on learning Python syntax, libraries, and best practices as fast as possible. I spent time building small examples, reading documentation, and applying what I learned directly into the project.

Because I already understood the process of learning a new language, I was able to adapt quickly and begin contributing to the team in a short amount of time.”

Salary expectations

I’m definitely open and flexible depending on the overall opportunity and responsibilities of the role. Given my enterprise software experience at Paycom and my background in backend and full stack development, I’d be looking for something competitive within the range budgeted for the position.

Tell me a time you faced a challenge or technical challenge?

Situation:
During my internship at Texas Instruments, I built a Python-based scraper to collect data from the TI E2E forums for our knowledge retrieval system.

Action:
One challenge I ran into was that the site would sometimes detect the scraper as automated traffic and return 403 errors. To solve that, I updated the scraper to better mimic normal browser behavior by adding a realistic user agent, introducing randomized delays between requests, and controlling concurrency so we weren’t sending too many requests at once. I also added error handling so restricted or failed pages could be skipped without breaking the overall pipeline.

Result:
That made the scraper much more reliable and allowed us to continue collecting large amounts of forum data in a stable way for downstream processing.

Can you tell me about your experience with algorithms?

I have experience with algorithms through both coursework and practical development work. In school I worked with common algorithms such as searching, sorting, and graph traversal while solving problems in C++ and Java. In my professional work, algorithmic thinking is applied when optimizing backend logic, improving query efficiency, and designing systems that process data efficiently.

How do algorithms help you when developing software?

Algorithms help ensure software runs efficiently and scales well. When designing a feature, I think about time complexity and how the system will perform as data grows. For example, selecting efficient search or filtering logic can significantly reduce processing time in backend services.

What data structures are you comfortable working with?

’Ive worked with common data structures such as arrays, linked lists, hash maps, stacks, queues, and trees. In practice, I often use hash maps and lists to efficiently store and retrieve data when building backend features or processing API responses.

When would you use a hash map instead of a list?

A hash map is useful when you need fast lookups by key, typically constant time complexity. A list is better when you primarily iterate through elements sequentially. Choosing the right data structure helps improve performance and readability of the code.

Do you have experience with CI/CD pipelines?

Yes. In my role at Paycom we used a Git-based workflow combined with Jira for tracking development tasks. When working on a feature or bug fix, I would create a branch and submit my changes through a pull request. After the code review was completed, automated tests would run through the CI pipeline. Once those passed, the code would be merged and deployed to a testing environment where we could validate the feature before it moved further in the release process.

How have you used Git in your development workflow?

I used Git daily for version control while working in an Agile environment. I created feature branches for tasks, committed changes, and submitted pull requests for code review. If conflicts occurred, I resolved them before merging so the codebase stayed stable.

Tell me about your experience working with REST APIs.

In my work at Paycom I interacted with REST APIs to retrieve and manage data between the frontend and backend. For example, when retrieving information for a job position, the API would use HTTP requests such as GET to retrieve resources like seats or position details, with identifiers such as a specific seat or position ID. My role involved implementing and handling those API requests so the frontend could properly display and update the data.

What is the difference between GET and POST?

Answer:
GET is used to retrieve data from a server without modifying it, while POST is used to send data to the server to create or update a resource.

What Programming Languages Are You Comfortable With?

I’m strongest in C++, Java, and PHP. My background in C++ and Java gave me a strong foundation in object-oriented programming, and at Paycom I worked primarily in PHP developing full-stack features and backend logic. Since PHP and Java share many similar concepts, it was easy for me to adapt quickly.

Tell me about a time you fixed a production issue.

Situation:
While working on the Position Management module at Paycom, I occasionally handled client-facing issues where something in the system wasn’t behaving correctly in production.

Action:
I would first reproduce the issue by reviewing logs and checking the API requests and database queries involved. After identifying the root cause, I implemented a fix in the backend logic and submitted it through our Git workflow for review and automated testing.

Result:
Once the fix passed testing, it was deployed through our CI/CD pipeline and resolved the issue for the client while maintaining stability in the rest of the system.

✅ 2. Why Schwab?

“What interests me about Schwab is the opportunity to work on large-scale systems that improve client experience through client centric innovations. I enjoy backend and full stack development, and I’m interested in continuing to grow in financial technology because of the complexity and impact those systems have.”

4. What experience do you have with Java?

“I have experience with Java primarily through coursework and academic projects, where I worked with object-oriented programming, data structures, and backend concepts. At Paycom, I also worked alongside teams that used Java and Spring-based backend services, so I became familiar with how enterprise Java applications and APIs are structured and integrated into larger systems.”

✅ 10. What experience do you have working in Agile?

“At Paycom, I worked in an Agile environment where we participated in sprint planning, standups, retrospectives, and collaborative development workflows. I worked closely with engineers and product teams to deliver features and resolve issues within sprint timelines.”

13. Do you have finance experience?

“Yes, I do have some finance-related experience from working at Paycom. I worked with systems that handled employee and HR-related data, including salary and position information, so I became comfortable working in environments where accuracy and data integrity were very important.

While I’m still growing my experience in the financial space, I’m very comfortable with analytical and data-driven work. I’ve always been strong in math and problem-solving, so I feel confident learning and adapting quickly in finance-focused technology environments.”

What do you know about spring boot ?

From my understanding, Spring Boot simplifies Java backend development by handling a lot of configuration automatically and making it easier to build REST APIs and enterprise services. I’m familiar with concepts like controllers, dependency injection, and service-based architecture.

I’m familiar with Spring Boot concepts through my exposure to enterprise backend development and Java coursework. At Paycom, I worked on backend systems and RESTful APIs, and while much of my direct work was in PHP-based services, the overall backend architecture concepts were very similar, such as handling API requests, business logic, service layers, and database interactions.

Because of that experience, I’m comfortable with how Spring Boot applications are structured and how backend services communicate and operate within larger systems. I’m confident I could ramp up quickly in a Spring Boot environment.

What do you know about cloud services ?

I have some exposure to cloud-based environments through projects and development workflows, including working with containerized applications and backend services that follow modern deployment patterns. I used several Azure services while working on a TI-sponsored AI knowledge retrieval project. We stored our Docker images in Azure Container Registry and deployed them using Azure Container Apps, which hosted services such as FastAPI, n8n, Open WebUI, and Qdrant. We used Azure Application Gateway for traffic routing, Azure Key Vault for managing secrets and API keys, and Azure Monitor for logging and performance monitoring. This allowed us to deploy a scalable RAG-based system that scraped TI forum data, stored embeddings in Qdrant, and generated responses using an LLM."

Difference between stack and queue?

“A stack is a LIFO data structure — last in, first out — like stacking plates. The last item added gets removed first. I’d use it for things like undo operations or DFS.

A queue is FIFO — first in, first out — like a line at a store. The first item added gets removed first. I’d use it for scheduling tasks or BFS.”

What is a class?

“A class is a blueprint for creating objects in object-oriented programming. It defines the data and behaviors an object can have.

For example, a Car class might have properties like color and speed, and methods like drive or brake.”

What is MVC ?

“MVC stands for Model-View-Controller. It’s a design pattern used to separate an application into different responsibilities to make the code easier to manage and scale.

The Model handles the data and business logic, the View is the user interface, and the Controller processes requests and connects the front end to the backend logic.

At Paycom, I worked mostly on the backend side, where controllers handled requests, services and models handled business logic and database interactions, and the frontend displayed the data to users.”

Tell me a time when requirements changed?

“At Paycom, I worked on a reusable job posting template feature. Initially, the requirement was just to add a dropdown where users could select an existing template.

Later in development, the requirements changed and the team wanted users to also be able to create new reusable templates directly from the UI using a plus icon next to the dropdown.

I adapted by creating a new backend API to handle template creation and then implemented the frontend JavaScript logic to connect the UI with the backend workflow.

The experience taught me the importance of being flexible with changing business requirements and communicating closely with the team to deliver a scalable solution.”

What is try catch and exception handling ?

“Exception handling is used to prevent applications from crashing when unexpected errors occur. A try-catch block lets you attempt risky code inside the try section, and if an error happens, the catch block handles it gracefully instead of stopping the program.

For example, if an API call or database query fails, you can catch the exception, log the error, and return a proper response to the user. At Paycom, exception handling was important for backend stability and debugging production issues.”

Experience with CSS,HTML, and JavaScript?

“At Paycom, I used HTML, CSS, and JavaScript together to build frontend functionality for a reusable template feature. HTML was used to create the dropdown and plus button in the UI. CSS was used to style the button so it matched the existing application design.

Then I used JavaScript with an event listener to handle the button click event. When the user clicked the plus icon, it called the backend API to create a new template and dynamically updated the dropdown without needing to refresh the page.”