Modern System Design Foundations

1. Introduction to System Design

• System: A set of interconnected components working together to achieve a specific goal.
  
• System Design: The process of defining the architecture, components, modules, interfaces, and data to satisfy specified requirements.
  
• Importance: Ensures scalability, reliability, maintainability, and performance in both hardware and software systems.
  

2. System Design Lifecycle

• Requirements Analysis
  
  • Functional vs Non-functional requirements
    
  • Stakeholder interviews and documentation
    
• System Specification
  
  • Defining the scope and boundaries
    
  • Input/output, processing, and storage needs
    
• Design Phases
  
  • High-Level Design (HLD): Architecture, technologies, data flow
    
  • Low-Level Design (LLD): Modules, interfaces, data structures
    

3. System Design Principles

• Modularity: Breaking the system into manageable, interchangeable components.
  
• Abstraction: Hiding complexity behind a simpler interface.
  
• Encapsulation: Bundling data with its operations.
  
• Separation of Concerns: Each component has a distinct responsibility.
  
• Loose Coupling and High Cohesion: Minimize dependencies while keeping related functionalities together.
  
• Scalability: Ability to grow in capacity.
  
• Fault Tolerance: Ensuring continuous operation during failures.
  

4. Architectural Patterns

• Monolithic Architecture
  
  • Single-tiered, tightly coupled
    
  • Easy to develop, hard to scale
    
• Layered Architecture
  
  • Presentation, Business, Data layers
    
• Client-Server Architecture
  
  • Separation of client logic and server logic
    
• Service-Oriented Architecture (SOA)
  
  • Services communicate via messages (e.g., SOAP)
    
• Microservices
  
  • Independently deployable services
    
  • Communication via APIs
    
• Event-Driven Architecture
  
  • Components react to events asynchronously
    

5. System Design Techniques

• Design Diagrams
  
  • UML (Use Case, Class, Sequence, Activity)
    
  • ER Diagrams for databases
    
  • Flowcharts for logic
    
• Data Flow Diagrams (DFDs)
  
  • Shows the movement of data within the system
    
• Entity-Relationship Models
  
  • Represents data structure and relationships
    
• API Design
  
  • REST, GraphQL, and RPC
    

6. Key Components in Modern Systems

• Databases: SQL vs NoSQL
  
• Load Balancers: Distribute requests for performance
  
• Caches: Reduce database load (e.g., Redis, Memcached)
  
• Message Queues: Decouples services (e.g., RabbitMQ, Kafka)
  
• Authentication and Authorization: OAuth2, JWT, SSO
  
• Monitoring and Logging: For debugging and performance insights
  

7. Non-Functional Requirements (NFRs)

• Scalability
  
• Reliability
  
• Availability
  
• Maintainability
  
• Security
  
• Performance
  

8. Cloud-Native System Design

• Cloud Providers: AWS, Azure, Google Cloud
  
• Containers: Docker
  
• Orchestration: Kubernetes
  
• Serverless Architecture: Functions as a Service (FaaS)
  
• CI/CD Pipelines: Continuous Integration/Deployment
  

9. Case Studies and Examples

• Design a URL Shortener
  
• Design an Online Education Platform
  
• Design a Scalable Messaging App
  
• Design a Payment Processing System
  

10. Best Practices

• Design for failure
  
• Always prototype first
  
• Document everything
  
• Use version control (e.g., Git)
  
• Automate testing and deployment