Senior full stack developer interview question and answers

1. What do the terms "Cluster" and "Non-Cluster" Indexes signify in PostgreSQL?

Cluster indexes are a form of index that PostgreSQL uses to organize data rows in a database according to their fundamental values. In a PostgreSQL database, a table can only have one clustering-based index. These clustered indexes can also determine the order in which the data is stored in the database. An RDBMS's primary key often enables you to build a clustered index based on just one column.

The data and its associated index are kept apart in non-clustered indexing. The pointer idea is used here; a pointer exists, pointing toward the data's position. Secondary indexing is another name for this kind of indexing. Many non-clustered indexes based on the supplied table may exist in a PostgreSQL database. Cluster indexing is more extensive when compared to non-cluster indexing.

2. State difference between blue/green deployment and rolling deployment

Example: Compared to the clone (blue), the green environment is active and handles all user traffic. A new version of an application can be sent to the blue environment for testing once it is prepared for release. Application traffic is changed from green to blue once the new release passes testing. When the next release is ready for testing, green goes idle, and blue takes over as the active production environment.

Example: If a new version needs to be installed on every node, it is installed on the first node while the remaining nodes manage end-user traffic. After the first node's new version has been installed, it will start controlling end-user traffic while the second node's new version is being set up. The procedure is done once more until all nodes have received the latest version upgrade.

3. What is referential transparency in functional programming?

Referential transparency is a fundamental concept in functional programming. It refers to a property of functions or expressions where a particular expression can be replaced with its resulting value without changing the overall behavior of the program.

In a referentially transparent program, every function or expression produces the same result for the same inputs, regardless of where and how it is used in the code. This property enables reasoning about functions' behavior and composition, making it easier to understand, test, and optimize functional programs.

Referential transparency allows for substituting function calls or expressions with their evaluated results. This means that if you have an expression x + y, and know the values of x and y, you can replace the expression with their sum without impacting the program's behavior.

4. What is the difference between normalization and denormalization?

Normalization and denormalization are two opposing strategies used in database design to optimize data organization and improve query performance. Here are the critical differences between normalization and denormalization:

1. Objective: The primary goal of normalization is to eliminate data redundancy and ensure data integrity.

2. Process: Normalization involves breaking down a database schema into multiple related tables to eliminate data duplication and dependency issues. It follows rules (known as standard forms) to ensure data is structured efficiently.

3. Data Duplication: Normalization minimizes data duplication by storing data in separate tables and establishing relationships through primary and foreign keys.

4. Update Anomalies: Normalization reduces update anomalies by maintaining data consistency. Changes to data only need to be made in one place.

5. Storage Efficiency: Normalization aims for better storage efficiency by minimizing data redundancy. It allows for efficient updates and insertions while maintaining data integrity.

6. Complexity: Normalized databases tend to have more tables and complex relationships, which can increase the complexity of queries and joins.

1. Objective: The primary goal of denormalization is to optimize query performance by reducing the number of joins and improving data retrieval speed.

2. Process: Denormalization involves combining related tables and duplicating data to reduce the need for joins and simplify queries. It introduces redundancy intentionally for performance gains.

3. Data Duplication: Denormalization increases data duplication by storing redundant data in multiple places for faster retrieval and reduced join operations.

4. Read Performance: Denormalization improves read performance by eliminating the need for complex joins and allowing for faster data retrieval, especially for complex queries.

5. Update Anomalies: Denormalization can introduce update anomalies, as changes to data may need to be made in multiple places to maintain consistency.

6. Storage Efficiency: Denormalization may increase storage requirements due to data redundancy, but it can improve performance by reducing the need for joint operations.

5. In Java, what is a connection leak? How can you fix this?

As a senior full-stack developer, there is a high chance you can be asked this full-stack developer interview question. In Java, a connection leak is when database connections are not correctly released or closed after their intended use. It occurs when connections are acquired from a connection pool but are not returned to the pool when they are no longer needed. Over time, this can lead to a depletion of available connections in the pool, causing performance issues and potentially leading to application failures.

6. What is event bubbling and capturing?

Event Bubbling: It is the default behavior in which an event is first triggered on the innermost element and then propagates upward through its ancestors in the DOM hierarchy. In other words, when an event occurs on a specific element, it is handled by that element's event handler first, then by its parent element, and so on, until it reaches the document level.

Event Capturing: It is the opposite of event bubbling. In event capturing, the event is first triggered on the outermost element and then propagates downward through its descendants in the DOM hierarchy. This mechanism allows you to intercept events at a higher level before they reach their target element.

7. What is MEAN Stack?

MEAN Stack is a popular software stack used for building web applications, which is why it becomes one of the most pertinent full-stack developer interview questions you can be asked. It is an acronym representing a collection of technologies: MongoDB, Express.js, Angular, and Node.js. Each component of the MEAN Stack serves a specific purpose, and together they enable developers to create end-to-end JavaScript-based web applications.

1. MongoDB: MongoDB is a NoSQL database that stores data in a flexible, JSON-like format called BSON (Binary JSON). It provides a scalable, high-performance, and schema-less data storage solution, making it well-suited for handling large amounts of data and accommodating dynamic requirements.

2. Express.js: Express.js is a web application framework for Node.js. It simplifies the process of building web applications by providing robust features for handling routes, middleware, and HTTP requests. Express.js helps create server-side logic and APIs that interact with the front end.

3. Angular: It is a popular front-end JavaScript framework developed by Google. It facilitates the development of dynamic and interactive single-page applications (SPAs). Angular provides a comprehensive set of tools, features, and best practices for building responsive user interfaces, managing data binding, and handling complex application logic.

4. Node.js: It is a JavaScript runtime built on Chrome's V8 JavaScript engine. It allows developers to run JavaScript code on the server side, enabling the creation of scalable and efficient server applications. Node.js provides an event-driven, non-blocking I/O model suitable for handling concurrent requests and building real-time applications.

8. Do you know how to stop a bot from utilizing your publically available API to scrape data?

It is technically impossible to stop data scraping as long as the API's data is publicly available. However, throttle or infrequent limiting can be used to reduce bot activity—automated computer programs that run on the internet and carry out specific tasks. A device won't be able to make any number of requests within a given timeframe because of constraints. A 429 Too Many Request HTTP error is generated if more requests than allowed are made. Since IP addresses are not unique to each device and potentially prevent the entire network from accessing the API, it is crucial to store more information than simply the device's IP address.

9. What security measures do you take to protect web applications from common vulnerabilities?

I prioritize security throughout the development process. I implement secure authentication and authorization mechanisms, such as bcrypt for password hashing and JWT for token-based authentication. Input validation and sanitization are performed to prevent common security risks like SQL injection and cross-site scripting (XSS). I also employ HTTPS and SSL certificates for secure communication. Regular security audits, vulnerability scanning, and staying updated with security best practices help ensure robust security measures.

10. Describe your experience with cloud platforms and how you leverage them in your projects.

I have extensive experience working with cloud platforms like AWS, Azure, and Google Cloud. I leverage cloud services to improve applications' scalability, reliability, and performance. I utilize services like AWS Lambda or Azure Functions for serverless computing, containerization with Docker and Kubernetes for efficient deployment, and managed database services for easy scalability and backups.

11. Describe your approach to designing and implementing RESTful APIs.

When designing RESTful APIs, I create a clear and consistent structure, adhering to REST principles. I use proper HTTP methods for different operations, such as GET, POST, PUT, and DELETE. I also ensure meaningful endpoint naming and resource representations. Security measures like authentication and authorization are integrated using standards like JWT. Additionally, I document the APIs comprehensively using tools like Swagger to facilitate easy integration and collaboration.

12. How do you ensure code quality and maintainability in your projects?

Code quality and maintainability are crucial. I follow industry best practices such as modularization, clean code principles, and SOLID design principles. I write unit tests for critical functionalities using testing frameworks like Jest or PHPUnit. Continuous integration and automated code analysis tools like SonarQube help identify issues early on. Regular code reviews and pair programming sessions improve code quality and knowledge sharing within the team.

13. Describe a complex web application or project you have worked on. What were the technical challenges you faced, and how did you overcome them?

In my previous role, I worked on a large-scale e-commerce platform that required significant technical expertise and posed several challenges. One of the critical technical challenges was optimizing the application's performance, especially during high-traffic periods.

To address this challenge, we employed various strategies. First, we thoroughly analyzed the application's codebase and database queries to identify potential bottlenecks. We then implemented caching mechanisms, both on the server side and client side, to reduce the number of requests and improve response times. This involved utilizing technologies like Redis for caching frequently accessed data and leveraging browser caching for static assets.

• Careful analysis

• Implementing performance optimizations

• Employing scalable architecture patterns

• Fostering a collaborative team environment