Technical Questions

Table of Contents

1. Architecture and Design Patterns

1.1. How does the 3-Tier Architecture pattern work?

Click to expand The 3-Tier Architecture separates an application into three layers: 1. Presentation Tier: The front-end or user interface (UI) that interacts with the user. 2. Logic Tier: The back-end or business logic layer where data processing and application logic occur. 3. Data Tier: The database layer where data is stored and managed. This separation helps organize code, making it more scalable, maintainable, and easier to manage.

1.2. How does the Hexagonal Architecture pattern work?

Click to expand Hexagonal Architecture separates the core business logic of an application from external systems (like databases or APIs). - Core: The central business logic. - Ports: Interfaces that allow external systems to communicate with the core. - Adapters: Implementations that connect the core to external systems. This makes the app easier to maintain, test, and adapt to new technologies.

1.3. How does the MVC pattern work?

Click to expand MVC (Model-View-Controller) splits an app into three parts: 1. Model: Manages data and business logic. 2. View: Displays data to the user. 3. Controller: Handles user input and updates the model or view. This separation makes the code easier to manage and scale.

1.4. How does Clean Architecture work?

Click to expand Clean Architecture separates an application into layers to keep the core business logic independent of external factors. The layers are: 1. Entities: Core business models. 2. Use Cases: Application-specific logic. 3. Interface Adapters: Convert data between external systems (like UI or database) and core logic. 4. Frameworks & Drivers: External tools and frameworks. This structure ensures flexibility, maintainability, and testability by keeping the core logic isolated from outside changes.

2. AWS and Serverless

2.1. What is Node.js and why is it commonly used for backend development?

Click to expand Node.js is an open-source JavaScript runtime built on Chrome's V8 engine. It's widely used for backend development because it’s non-blocking and event-driven, which allows it to handle many requests simultaneously. This makes it ideal for real-time applications like chat apps or APIs that need to process many I/O operations without slowing down.

2.2. How does AWS Lambda work, and what are its main benefits?

Click to expand AWS Lambda is a serverless service that lets you run code without managing servers. You upload your code, and Lambda automatically handles scaling based on incoming requests. Its key benefits are: - Cost Efficiency: You only pay for compute time. - Automatic Scaling: It scales based on demand. - No Server Management: No need to manage infrastructure. Lambda is ideal for event-driven tasks like API requests, file uploads, or database triggers.

2.3. What is the best architecture for small Node.js applications using AWS?

Click to expand For small Node.js apps, a serverless architecture is often the best choice. Using AWS Lambda with API Gateway allows you to run code in response to HTTP requests without managing servers. This setup automatically scales based on traffic, and combined with services like DynamoDB for storage and S3 for files, it offers a cost-effective and low-maintenance solution ideal for small apps.

2.4. Why use Serverless? What are its advantages?

Click to expand Serverless eliminates infrastructure management, automatically scales with demand, and reduces costs by charging only for actual usage. It's ideal for building scalable, event-driven applications quickly, allowing developers to focus on writing code instead of managing servers.

2.5. When to use Kubernetes and when to use Serverless?

Click to expand - Kubernetes is ideal when you need full control over your infrastructure, want to orchestrate containerized applications, or have complex microservices architectures that require stateful services, custom networking, and fine-grained scaling. - Serverless is the best choice for event-driven workloads where you don’t want to manage infrastructure. It’s suitable for applications that need automatic scaling, easy event processing, and cost savings by paying only for the resources consumed. In general, Kubernetes is more suitable for large, complex systems, while serverless is ideal for simpler applications or where infrastructure management is not a concern.

2.6. When to use Docker?

Click to expand Docker is useful when you need to package applications and their dependencies into a container for consistency across different environments. It is ideal for: - Microservices architectures. - Development environments where you want to ensure consistency between local and production setups. - CI/CD pipelines where you need to ensure that code runs consistently regardless of the environment. - Portability across platforms, as Docker containers run the same on any machine that supports Docker.

3. Debugging and Problem Solving

3.1. How do you approach debugging a complex issue?

Click to expand My process involves breaking the issue into smaller parts to isolate the root cause. I: - Review logs and replicate the problem in a test environment. - Use debugging tools and systematically test hypotheses until the issue is resolved.

3.2. What are the best approaches to resolve the typical timeout problem caused when a Lambda function triggered by API Gateway exceeds 30 seconds while managing large data, resulting in a 504 timeout?

Click to expand To avoid timeouts with large data in Lambda, use SQS or Step Functions: - SQS: Send tasks to an SQS queue for asynchronous processing, avoiding API Gateway timeouts. - Step Functions: Break the task into smaller steps, allowing multiple Lambdas to process data without hitting time limits. Both methods prevent 504 timeouts by handling data processing in the background.

4. General Development Practices

4.1. What is Infrastructure as Code (IaC)?

Click to expand Infrastructure as Code (IaC) is the practice of managing and provisioning infrastructure using code instead of manual processes. It allows developers to define servers, networks, databases, and other resources in configuration files, making deployments consistent, repeatable, and version-controlled. Tools like Terraform, AWS CloudFormation, and Ansible are commonly used for IaC.
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4.3. What is the best practice to manage a growing monolithic architecture with 1000+ files of code?

Click to expand The best approach is to shift to a microservices architecture, where the monolith is broken into smaller, independent services. This enhances scalability, maintainability, and resilience. Changes in one service don’t affect others, limiting issues to individual services and reducing system-wide downtime. You can update and deploy services independently without impacting the entire system.

4.4. What are the advantages of a monolithic architecture?

Click to expand Monolithic architecture is simpler to develop and test, especially for small applications. All components are in one codebase, so there's no need for complex inter-service communication. It's easier to debug and can be more efficient for smaller systems, as there’s less overhead.

4.5. What is a REST API?

Click to expand A REST API uses HTTP methods (GET, POST, PUT, DELETE) to allow communication between clients and servers. It is stateless, meaning each request is independent, and is known for its simplicity, scalability, and flexibility.

4.6. What is a SOAP API?

Click to expand A SOAP API is a protocol for exchanging structured information using XML over HTTP, SMTP, or other transport protocols. It enforces strict standards for security and error handling, making it reliable for enterprise use.

4.7. What is GraphQL?

Click to expand GraphQL is a query language for APIs that allows clients to request exactly the data they need. Unlike REST, it uses a single endpoint and reduces data over-fetching and under-fetching.

4.8. What is the difference between SQL and NoSQL?

Click to expand - SQL: Relational databases with structured tables and predefined schemas (e.g., MySQL, PostgreSQL). - NoSQL: Non-relational databases with flexible formats, ideal for unstructured data and scalability (e.g., MongoDB, DynamoDB).

4.9. What is CI/CD and its advantages?

Click to expand CI/CD automates code integration, testing, and deployment. - Continuous Integration: Regularly merges code with automated tests. - Continuous Deployment: Automatically deploys approved changes. Advantages: - Faster delivery. - Fewer errors through automation. - Quick feedback and iteration.

4.10. What is the difference between TypeScript and JavaScript?

Click to expand - JavaScript: Dynamic, loosely typed, used for web development. - TypeScript: Adds static typing for error prevention, compiles to JavaScript, and is better for large projects.

4.11. Why should we use frameworks?

Click to expand Frameworks offer structure, scalability, and reusable components, allowing developers to focus on the business logic rather than reinventing basic features. They help enforce best practices and reduce development time while ensuring consistency and maintainability in large projects.

4.12. What are the pros and cons of Express.js?

Click to expand - Pros: - Unmatched popularity and a huge ecosystem of extensions. - Simple to learn and use, with a wealth of tutorials. - Cons: - Outdated mechanics, lacking native async/await support. - Slower than alternatives and not actively maintained.

4.13. What are the pros and cons of Nest.js?

Click to expand - Pros: - Feature-rich, covers many application concerns, including message queues. - Great for teams familiar with OOP principles and frameworks like Spring or Angular. - Well-documented with a vibrant community. - Cons: - Steeper learning curve due to its opinionated structure and complex abstractions. - Increased complexity for teams not experienced in advanced JavaScript.

4.14. What are the pros and cons of Fastify?

Click to expand - Pros: - Fast, lightweight, and based on Node.js/JavaScript standards. - Easy to learn with minimal overhead. - Cons: - Smaller ecosystem and community compared to Express.js and Nest.js.

4.15. When should you use Nest.js, Express.js, or Fastify?

Click to expand - Express.js: Best for projects that need full control over the application and are built by experienced architects. It's simple and has an extensive ecosystem of middleware but may require more effort to cover advanced application concerns. - Nest.js: Ideal for large applications that benefit from an Object-Oriented Programming (OOP) approach, such as those with complex business logic or teams experienced with Java/Spring/Angular. It's feature-rich and well-suited for large-scale apps. - Fastify: A good choice for smaller apps or microservices that need to be fast and lightweight. It is Node.js/JavaScript standards-based with a shallow learning curve, but it is not as popular as Express.js or Nest.js.