System Design Process

The system design process is a structured approach to developing software architecture that can meet both functional and non-functional requirements. It involves understanding the problem, gathering the necessary requirements, designing the system at both high and low levels, and validating the design to ensure that it will perform well in real-world conditions. A well-executed system design process results in a scalable, reliable, and maintainable system.

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1. Gathering Requirements

The first step in the system design process is to gather and understand the requirements. This is critical because the entire system design will be built around these requirements.

Steps Involved:

• Functional Requirements:
  • These are the features and capabilities the system must provide. For example, in an e-commerce platform, functional requirements might include the ability to browse products, add items to a cart, checkout, and make payments.
• Non-Functional Requirements:
  • These define the system’s quality attributes, such as scalability, availability, performance, security, and maintainability. For instance, an online streaming service might need to support thousands of concurrent video streams with low latency.
• Stakeholder Inputs:
  • It’s essential to consult stakeholders, including users, product managers, and business teams, to ensure the system addresses both their needs and goals.
• Technical Constraints:
  • Understanding technical limitations such as database size, network bandwidth, and third-party integration APIs that might affect design decisions.

Tools for Gathering Requirements:

• Interviews: Talking directly with stakeholders or clients to understand their needs.
• Surveys/Questionnaires: Collecting structured feedback from users or business teams.
• Use Case Diagrams: Visual representation of how users will interact with the system.

Example:

For a social media platform, gathering requirements would involve understanding user needs (posting content, commenting, following users) and business needs (ad placement, content moderation, analytics).

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2. Defining Key Use Cases and Constraints

Once the requirements are clear, the next step is to identify key use cases and any constraints that might influence how the system should function. This step helps narrow down the design decisions and ensures the system will meet both functional and non-functional goals.

Steps Involved:

• Use Case Identification:
  • Define the most common or critical scenarios in which the system will be used. These scenarios help guide the design by focusing on what the system needs to do under different conditions.
  • Example Use Case: In an e-commerce platform, use cases might include:
    • Browse Products: Users search and filter products.
    • Add to Cart: Users add items to their shopping cart.
    • Make Payment: Users proceed to checkout and pay for their order.
• Defining Constraints:
  • Performance Constraints: e.g., Response time for searches should be under 2 seconds.
  • Security Constraints: e.g., Must adhere to GDPR for user data privacy.
  • Legal Constraints: e.g., Content licensing issues in streaming platforms.
  • Technical Constraints: e.g., A system must be built using specific technologies or integrations (e.g., AWS, MongoDB, etc.).
• Prioritization:
  • Not all use cases and constraints are equally important. Prioritize critical use cases that align with business goals and user needs, while balancing technical and legal constraints.

Example:

For a video streaming platform, the key use cases would involve:

• Streaming video with minimal buffering.
• Handling user logins and subscriptions.
• Delivering personalized content recommendations. And constraints like ensuring GDPR compliance and content licensing restrictions would influence both functional and non-functional requirements.

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3. Designing High-Level Architecture and Low-Level Components

Once the requirements and constraints are understood, the next step is to design the system’s high-level architecture and then dive into the low-level components.

High-Level Architecture Design:

• Objective: Provide an overview of the system, showing how the major components interact with each other.

• Components to Include:

  • Client Layer: User interface (e.g., web, mobile).
  • Web Layer: Where the application logic resides (e.g., Node.js, Flask).
  • Database Layer: Where data is stored (e.g., relational, NoSQL).
  • Service Layer: Microservices or services that manage specific business logic (e.g., payment service, recommendation service).
  • External Integrations: Third-party services like payment gateways, email services, or CDNs.
  • APIs: To facilitate communication between different services and external integrations.

• Example:
  For an e-commerce platform, the high-level architecture would include:

  • Frontend (React/Angular) interacting with a Backend (Node.js/Express) that communicates with databases (SQL/NoSQL) and external payment gateways (Stripe, PayPal).

• Diagrams: High-level architecture diagrams, such as Entity Relationship Diagrams (ERD) or Component Diagrams, help visualize these components.

Low-Level Component Design:

• Objective: Define the specifics of individual components, including their interactions, data models, and algorithms.
• Components to Include:
  • Database Schemas: How data is structured (tables, relationships, indexing).
  • API Specifications: What endpoints are required, what data they accept and return.
  • Algorithms: Logic behind features, like recommendations or search algorithms.
  • Error Handling and Failover: How the system handles errors or failures (e.g., retry mechanisms, fallback procedures).
• Example: For a payment system in an e-commerce platform:

  • Database Schema:

    CREATE TABLE Payments (
      payment_id UUID PRIMARY KEY,
      order_id UUID REFERENCES Orders(order_id),
      amount DECIMAL(10, 2),
      payment_method ENUM('credit_card', 'upi', 'wallet'),
      status ENUM('pending', 'completed', 'failed'),
      created_at TIMESTAMP
    );
    

  • API Endpoint: /processPayment which accepts payment details and returns a status (success/failure).
  • Payment Algorithm: The system will interact with external APIs like Stripe to process payments, with retry logic in case of network failure.