All Roadmaps›⚛️ React Mastery›Phase 15›System Design & Architecture

System Design & Architecture

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📖 Concept

As a senior developer, you're not just writing components; you're designing systems.

Key Architectural Decisions:

  1. State Management Strategy: When to use local vs. global vs. server state.
  2. Component Library vs. Custom UI: Deciding based on project requirements and team size.
  3. Monorepo vs. Multi-repo: Organizing large codebases with multiple apps and shared packages.
  4. Data Fetching Layer: Standardizing how the app communicates with the backend (interceptors, error handling).

The 'Clean Architecture' in React: Keep your UI layer as "dumb" as possible. Extract business logic into hooks or services. This makes your app easier to test, refactor, and migrate to new frameworks in the future.

Design Systems: A senior developer should understand how to translate a Figma design into a token-based system (colors, spacing, typography) that is consistent across the entire application.

💻 Code Example

codeTap to expand ⛶
1/* 
2Example of a decoupled "Feature" architecture:
3

4/features/auth
5  /api              # API calls (services)
6    login.ts
7  /components       # UI components
8    LoginForm.tsx
9  /hooks            # State and business logic
10    useLogin.ts
11  /types            # TypeScript interfaces
12    auth.types.ts
13  /utils            # Feature-specific helpers
14    token-handler.ts
15  index.ts          # The public API for this feature
16*/
17

18// --- index.ts (Public API) ---
19// Only export what is absolutely necessary
20export { useAuth } from './hooks/useAuth';
21export { LoginForm } from './components/LoginForm';
22export type { User } from './types/auth.types';
23

24// --- useLogin.ts (Decoupled Logic) ---
25import { useMutation } from '@tanstack/react-query';
26import { loginApi } from '../api/login';
27

28export const useLogin = () => {
29  return useMutation({
30    mutationFn: loginApi,
31    onSuccess: (data) => {
32      // Handle success (save token, redirect)
33    },
34    onError: (err) => {
35      // Handle error (notify user)
36    }
37  });
38};

🏋️ Practice Exercise

  1. Design the architecture for a 'Global E-commerce Dashboard' from scratch. Explain your choice of state management and routing.
  2. Create a 'Theming System' using CSS Variables that can be changed at runtime.
  3. Review an old project and refactor a giant component into a decoupled structure (API, Hooks, UI).
  4. Lead a mock 'Architecture Review' with a colleague, defending your choice of technical stack.

⚠️ Common Mistakes

  • Prematurely choosing a complex tool (like Redux) when simpler tools would suffice.

  • Not standardizing the 'Data Flow' of the application.

  • Mixing business logic directly into the JSX.

  • Not considering 'Cross-Cutting Concerns' like logging, error tracking, and analytics.

💼 Interview Questions

🎤 Mock Interview

Practice a live interview for System Design & Architecture

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