Tuesday, July 2, 2024

System Design Concepts and Interview FAQs

System Design involves creating the architecture of a system, considering aspects like scalability, reliability, performance, and maintainability. Here are some core concepts and industry-standard architectures:

Core Concepts in System Design

  • Scalability: The ability of a system to handle increased load by adding resources.
    • Vertical Scaling: Adding more power (CPU, RAM) to an existing machine.
    • Horizontal Scaling: Adding more machines to handle the load.
  • Reliability: Ensuring the system operates correctly even in case of failures.
    • Redundancy: Duplicate critical components or functions to increase system reliability.
    • Failover: Automatic switching to a backup system if the primary system fails.
  • Performance: The system’s ability to handle requests within acceptable time limits.
    • Caching: Storing frequently accessed data in a temporary storage for quick retrieval.
    • Load Balancing: Distributing incoming network traffic across multiple servers.
  • Maintainability: Ease of making changes and extending the system.
    • Modular Design: Dividing a system into smaller, manageable modules.
    • Documentation: Keeping detailed and up-to-date documentation of the system.
  • Security: Protecting the system and data from unauthorized access and breaches.
    • Authentication: Verifying the identity of users or systems.
    • Authorization: Granting permission to resources based on user roles.

Industry-Standard System Design Architectures

  • Monolithic Architecture: All components of the system are packaged together.
    • Easy to develop and deploy initially but can become difficult to manage and scale as the system grows.
  • Microservices Architecture: Breaks down a system into smaller, independent services that communicate via APIs.
    • Facilitates scalability, maintainability, and allows teams to work independently.
  • Event-Driven Architecture: System components communicate through events, enabling asynchronous processing.
    • Useful for applications with complex workflows and real-time updates.
  • Service-Oriented Architecture (SOA): Similar to microservices but with more emphasis on service reusability and communication via an enterprise service bus (ESB).
    • Common in large enterprises with complex IT landscapes.
  • Serverless Architecture: Applications are deployed on third-party servers and managed by cloud providers.
    • Simplifies operations, reduces costs, and allows developers to focus on code without worrying about infrastructure.
  • Layered (N-Tier) Architecture: Organizes the system into layers (presentation, business logic, data access).
    • Promotes separation of concerns and ease of maintenance.
  • Peer-to-Peer (P2P) Architecture: Decentralized architecture where each node (peer) can act as both a client and server.
    • Common in file-sharing and blockchain technologies.
  • Client-Server Architecture: Divides the system into two parts: client (frontend) and server (backend).
    • The server provides services to client requests, commonly used in web applications.

Popular System Designs

  • URL Shortener (e.g., bit.ly)
    • Generate a short, unique alias for a long URL.
    • Handle redirects efficiently.
  • Designing a Web Crawler
    • Traverse the web to collect information for indexing.
    • Handle distributed crawling and data storage.
  • Social Media Feed (e.g., Twitter, Facebook)
    • Display posts from friends/followed users.
    • Efficiently update and retrieve feed content.
  • Messaging System (e.g., WhatsApp, Facebook Messenger)
    • Real-time messaging between users.
    • Manage message delivery, read receipts, and offline storage.
  • Distributed File Storage (e.g., Google Drive, Dropbox)
    • Store and retrieve large amounts of data.
    • Handle replication, consistency, and data retrieval.
  • Ride Sharing Service (e.g., Uber, Lyft)
    • Match riders with drivers in real-time.
    • Handle location tracking, ride pricing, and user management.
  • Video Streaming Service (e.g., YouTube, Netflix)
    • Stream video content to users.
    • Handle video storage, encoding, CDN distribution, and playback.
  • E-commerce Platform (e.g., Amazon, eBay)
    • Manage product listings, shopping carts, and orders.
    • Handle search, recommendation, and payment processing.
  • Search Engine (e.g., Google)
    • Index and search the web for relevant information.
    • Handle ranking algorithms, crawling, and query processing.
  • Notification System (e.g., Email , SMS notifications)
    • Send notifications to users.
    • Handle user preferences, delivery guarantees, and scaling.

FAQs in System Design Interviews

  • What is the difference between vertical and horizontal scaling?
    • Vertical scaling involves adding more resources (CPU, RAM) to an existing machine.
    • Horizontal scaling involves adding more machines to handle the load.
  • How would you design a system to handle a large number of read/write operations?
    • Use caching to reduce read load.
    • Implement sharding to distribute the write load.
    • Consider using a NoSQL database for high write throughput.
  • How do you ensure high availability in a distributed system?
    • Implement redundancy and failover mechanisms.
    • Use load balancers to distribute traffic.
    • Design for fault tolerance by replicating data across multiple nodes.
  • What is eventual consistency?
    • Eventual consistency means that, given enough time, all replicas of a distributed system will converge to the same state.
  • How would you design a rate limiter?
    • Use techniques like token bucket or leaky bucket.
    • Store rate limiting information in a distributed cache (e.g., Redis).
  • What are the trade-offs between consistency and availability in a distributed system?
    • According to the CAP theorem, you can only achieve two out of three: consistency, availability, and partition tolerance.
    • Choosing consistency means you may sacrifice availability during network partitions.
    • Choosing availability means you may have eventual consistency.
  • How would you design a scalable search engine?
    • Use inverted indexes for fast search lookups.
    • Implement distributed crawling and indexing.
    • Use ranking algorithms to provide relevant search results.
  • What is a CDN and how does it work?
    • A Content Delivery Network (CDN) caches content at various edge locations to reduce latency and load on the origin server.
    • It helps in faster content delivery by serving content from a location closer to the user.
  • How do you handle database replication?
    • Use master-slave replication or master-master replication.
    • Ensure data consistency with techniques like two-phase commit or conflict resolution strategies.
  • What are the considerations for designing a caching system?
    • Decide what data to cache based on access patterns.
    • Choose an appropriate eviction policy (e.g., LRU, LFU).
    • Handle cache invalidation strategies to maintain data consistency.

These examples and questions should give you a good foundation for understanding system design and preparing for interviews.


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