System-Design-Question

Created basic System Design Round UI in mock interview

Category: system_design Date: 2026-03-08

System Design Round UI Mock Interview Solution

Problem Statement: Design a UI for a mock interview system that allows users to create and manage interview questions, schedule interviews, and view interview results.

First Principle of System Design: The first principle of system design emphasizes the importance of Separation of Concerns (SoC). It suggests that a system should be divided into distinct components, each with its own responsibility, to promote modularity, maintainability, and scalability.

Requirements (Functional + Non-functional)

  1. Functional Requirements:
    • Create and manage interview questions
    • Schedule interviews
    • View interview results
    • User authentication and authorization
    • Search and filtering of interview questions
  2. Non-functional Requirements:
    • High availability (99.99% uptime)
    • Scalability ( handle 1000+ concurrent users)
    • Performance (response time < 500ms)
    • Data security and integrity

High-Level Architecture

  1. Frontend:
    • Client-side: React.js or Angular.js for building the UI
    • Server-side: Node.js with Express.js for handling API requests
  2. Backend:
    • Database: MongoDB or PostgreSQL for storing interview questions, user data, and interview results
    • API Gateway: NGINX or Amazon API Gateway for routing API requests
  3. Infrastructure:
    • Cloud provider: AWS or Google Cloud for scalability and high availability
    • Load balancer: HAProxy or Amazon Elastic Load Balancer for distributing traffic

Database Design

  1. User Collection:
    • _id (primary key)
    • username
    • password (hashed)
    • email
  2. Interview Question Collection:
    • _id (primary key)
    • question_text
    • category
    • difficulty_level
  3. Interview Result Collection:
    • _id (primary key)
    • user_id (foreign key referencing User Collection)
    • interview_question_id (foreign key referencing Interview Question Collection)
    • result (pass/fail)

Scaling Strategy

  1. Horizontal Scaling:
    • Add more instances of the application server, load balancer, and database to handle increased traffic
    • Use a auto-scaling service (e.g., AWS Auto Scaling) to dynamically adjust instance count based on demand
  2. Vertical Scaling:
    • Upgrade instance types (e.g., from t2.micro to c4.xlarge) to increase CPU and memory resources
    • Use a load balancer to distribute traffic across multiple instances

Bottlenecks

  1. Database Performance:
    • Use an optimized database index on the interview question collection
    • Implement caching (e.g., Redis) to store frequently accessed data
  2. API Gateway Performance:
    • Use a content delivery network (CDN) to cache static assets
    • Implement rate limiting and IP blocking to prevent abuse

Trade-offs

  1. Database Choice:
    • MongoDB provides a flexible schema, but may impact performance and data consistency
    • PostgreSQL provides strong consistency, but may require more configuration and maintenance
  2. Frontend Framework:
    • React.js provides a fast and efficient development experience, but may require more configuration and optimization
    • Angular.js provides a robust and feature-rich framework, but may be overkill for a simple UI

Learning Links:

  1. Separation of Concerns (SoC): https://en.wikipedia.org/wiki/Separation_of_concerns
  2. Microservices Architecture: https://en.wikipedia.org/wiki/Microservices
  3. Database Indexing: https://en.wikipedia.org/wiki/Index_(database)
  4. Caching: https://en.wikipedia.org/wiki/Cache_(computing)
  5. Load Balancing: https://en.wikipedia.org/wiki/Load_balancing_(computing)
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