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Day 1 - Introduction to System Design

What Is System Design?

System design is the process of defining the architecture, components, modules, interfaces, and data for a system to satisfy specified requirements. It's about building software and hardware systems that are scalable, reliable, and maintainable.

Why Is System Design Important?

  • Scalability: Systems can handle growth in users, data, and transactions.
  • Reliability: Systems work consistently under different conditions.
  • Maintainability: Systems can be updated and fixed easily without major downtime.
  • Performance: Systems respond quickly and efficiently to user requests.

Types of Systems

  • Simple systems: Small apps or services with limited users and features (e.g., a to-do list app).
  • Distributed systems: Multiple machines working together (e.g., Netflix, Facebook).
  • Real-time systems: Systems requiring immediate processing (e.g., Uber ride tracking).
  • Batch systems: Process large data in chunks at intervals (e.g., payroll systems).

Key System Design Principles

  1. Modularity: Break system into smaller, independent modules.
  2. Separation of Concerns: Each module handles a specific responsibility.
  3. Scalability: Design to handle growing loads smoothly.
  4. Fault Tolerance: System continues operating despite failures.
  5. Consistency & Availability: Manage trade-offs depending on use case (we'll cover CAP theorem later).
  6. Simplicity: Prefer simple designs over complicated ones for easier maintenance.

Visual: System Design Overview Diagram

Here's a high-level diagram showing the main components in a typical scalable system:

  • Client Layer: User interface (mobile app, browser)
  • API Layer: Handles client requests, routes them to appropriate services
  • Service Layer: Core business logic processing
  • Data Layer: Databases, caches, and storage systems
  • Infrastructure: Load balancers, messaging queues, CDNs

Here's a clear and simple System Design Overview Diagram to illustrate the main components of a typical scalable system:

+-----------------+           +-----------------+          +------------------+
|                 |           |                 |          |                  |
|    Client       |  <------> |     API Layer   | <------>  |   Service Layer  |
|  (Browser/App)  |           | (Load Balancer, |          | (Business Logic) |
|                 |           |   API Gateway)  |          |                  |
+-----------------+           +-----------------+          +------------------+
                                                          /          |           \
                                                         /           |            \
                                               +------------+  +------------+  +------------+
                                               |   Cache    |  |  Database  |  | Messaging  |
                                               |  (Redis)   |  | (SQL/NoSQL)|  |  Queue     |
                                               +------------+  +------------+  +------------+

Explanation:

  • Client: The user interface, such as a web browser or mobile app.
  • API Layer: Manages incoming requests, includes load balancers and API gateways.
  • Service Layer: Contains the core application logic and services.
  • Cache: Temporary storage to speed up frequent data retrieval.
  • Database: Persistent storage for structured or unstructured data.
  • Messaging Queue: Handles asynchronous communication between services.

If you want, I can generate a polished, graphic version of this diagram for you! Would you like me to do that?

Quick Exercise:

Think of an app you use frequently (e.g., Instagram, Amazon). What do you think are the main components involved in that system? Jot down a rough list or sketch a simple diagram.