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System Design

System design is the process of defining the architecture, components, modules, interfaces, and data for a system to satisfy specified requirements. It is a critical skill for building scalable, reliable, and maintainable software systems, especially at scale.

🧩 Key Concepts​

  • Scalability: Ability of a system to handle increased load by adding resources.
  • Reliability: Ensuring the system works correctly and consistently over time.
  • Availability: The proportion of time a system is operational and accessible.
  • Maintainability: Ease of updating and improving the system.
  • Performance: How quickly a system responds to requests.
  • Consistency: Ensuring data remains accurate and synchronized across the system.
  • Partition Tolerance: System’s ability to continue operating despite network partitions (see CAP theorem).

🏗️ Common Components​

  • Load Balancer: Distributes incoming traffic across multiple servers.
  • Database: Stores and manages data (SQL, NoSQL, caching).
  • Cache: Temporarily stores frequently accessed data for faster retrieval.
  • Application Server: Runs the core business logic.
  • Message Queue: Enables asynchronous communication between services.
  • CDN (Content Delivery Network): Delivers static content closer to users.

🛠️ Design Principles​

  • Separation of Concerns: Divide the system into distinct sections, each handling a specific responsibility.
  • Redundancy: Duplicate critical components to prevent single points of failure.
  • Horizontal Scaling: Add more machines to handle increased load.
  • Vertical Scaling: Increase resources (CPU, RAM) on existing machines.
  • Statelessness: Design services so they don’t rely on local state, making scaling easier.

📚 Useful Links​

📝 Notes​

  • System design interviews often focus on trade-offs and justifying your choices.
  • Practice designing systems like URL shorteners, chat apps, and news feeds.
  • Always consider requirements, constraints, and bottlenecks.