System Design – Interview Questions

  1. What is the purpose of software system design?
    Software system design aims to transform user requirements into a well-organized and structured solution by defining system architecture, modules, interfaces, and other components.
  2. Explain the difference between monolithic and microservices architectures.
    Monolithic architecture is a single, tightly integrated application, while microservices use small, independent services communicating through APIs. Example: Monolithic – A traditional web application; Microservices – Netflix architecture.
  3. How do you decide between a relational database and a NoSQL database for a specific application?
    Use a relational database when data consistency and strong ACID properties are crucial. Use NoSQL databases when scalability and flexible schema are required. Example: Relational – Banking application; NoSQL – Real-time analytics platform.
  4. What is the role of load balancing in a distributed system?
    Load balancing distributes incoming network traffic across multiple servers to ensure optimal resource utilization and prevent overload on any single server. Example: Nginx for distributing web traffic across application servers.
  5. How can you ensure data security in a distributed system?
    Implement encryption, authentication, and authorization mechanisms, use secure communication protocols (e.g., HTTPS), and regularly update security patches. Example: Using SSL/TLS for securing data transmission in a distributed e-commerce system.
  6. Explain the concept of caching and its significance in software system design.
    Caching stores frequently accessed data in a temporary storage, reducing the need to fetch the same data repeatedly from the original source, which improves system performance. Example: Caching frequently accessed database query results in a web application.
  7. Describe the “Database Sharding” technique and when it’s useful.
    Database sharding involves horizontally partitioning data across multiple databases to handle large datasets and improve scalability. It’s useful when a single database becomes a performance bottleneck. Example: Sharding user data based on geographical regions in a global social media platform.
  8. What are design patterns, and how do they benefit software system design?
    Design patterns are reusable solutions to common software design problems. They enhance system maintainability, scalability, and code quality. Example: Singleton pattern to ensure only one instance of a class exists.
  9. Explain the role of an API gateway in a microservices architecture.
    An API gateway acts as a single entry point for client requests, routing them to appropriate microservices. It handles tasks like authentication, rate limiting, and request/response transformations. Example: Netflix Zuul as an API gateway for their microservices.
  10. What is event-driven architecture, and why is it popular in modern systems?
    Event-driven architecture enables communication between components through events, facilitating loose coupling and scalability. It is popular because it enables real-time processing, responsiveness, and adaptability. Example: Using Apache Kafka for real-time data streaming and processing in a financial trading platform.
  11. How can you ensure high availability in a distributed system?
    Ensure redundancy through replication, utilize load balancing, implement failover mechanisms, and design for fault tolerance. Example: Using a distributed database with replication across multiple data centers for high availability.
  12. Discuss the pros and cons of a RESTful API compared to a GraphQL API.
    RESTful API pros: Simplicity, standardized, statelessness. Cons: Over-fetching, under-fetching. GraphQL pros: Flexibility, efficient data retrieval. Cons: Complexity. Example: RESTful API for a basic CRUD application; GraphQL API for a data-intensive application with complex data needs.
  13. What are the key considerations when designing a scalable system?
    Vertical and horizontal scaling, load balancing, caching, statelessness, and sharding. Example: Designing a scalable e-commerce platform that can handle an increasing number of users and transactions.
  14. Explain the role of Docker in software system design and deployment.
    Docker facilitates containerization, allowing applications to run consistently across different environments and simplifying deployment and scaling processes. Example: Dockerizing a web application to ensure it runs the same way in development, testing, and production environments.
  15. How can you optimize the performance of a database query?
    Optimize database indexes, minimize database joins, use database caching, and denormalize data when necessary. Example: Adding indexes to frequently queried columns in a relational database.
  16. Describe the principles of the SOLID design principles.
    SOLID stands for Single Responsibility Principle, Open/Closed Principle, Liskov Substitution Principle, Interface Segregation Principle, and Dependency Inversion Principle. These principles enhance code maintainability, extensibility, and readability. Example: Following the Single Responsibility Principle by separating UI logic from business logic in an application.
  17. How can you ensure data consistency in a distributed system?
    Use distributed transactions or implement eventual consistency through mechanisms like CRDTs (Conflict-Free Replicated Data Types). Example: Implementing distributed transactions for multi-region writes in a banking application.
  18. Explain the role of an Application Load Balancer (ALB) in cloud-based systems
    An ALB distributes incoming application traffic across multiple targets (e.g., EC2 instances) within an Auto Scaling group, ensuring high availability and fault tolerance. Example: Using AWS Application Load Balancer to distribute incoming HTTP traffic across EC2 instances hosting a web application.
  19. How do you handle long-running tasks in a web application?
    Use background processing or task queues to handle long-running tasks asynchronously, freeing up resources for other requests. Example: Using Celery with RabbitMQ as a task queue to process image uploads in a social media application.
  20. Discuss the differences between synchronous and asynchronous communication in distributed systems.
    Synchronous communication waits for a response before proceeding, while asynchronous communication continues without waiting for an immediate response. Asynchronous communication is often preferred for scalability and responsiveness. Example: Synchronous – Traditional HTTP request-response; Asynchronous – Messaging systems like RabbitMQ or Apache Kafka.

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