Context API V/s Redux Toolkit

Context API vs Redux Toolkit in React — both are used for state management, but they solve slightly different problems.

⚡ Context API

• ✅ What it is:

  • A built-in feature in React for passing data through the component tree without prop drilling.
  • Good for small or medium apps where global state is limited. (eg: theme, user auth, language, etc)

• ✅ How it works:

  • Create a context.
  • Wrap the component with a Provider to share state.
  • Consume state using useContext.

• Example:

      const ThemeContext = React.createContext();
      const App = () => {
          const [theme, setTheme] = React.useState('light')
          return(
              <ThemeContext.Provider value={{theme, setTheme}}>
                  <Child/>
              </ThemeContext.Provider>
          )
      }
  
      const Child = () => {
          const {theme, setTheme} = React.useContext(ThemeContext)
          return (
              <div>
                  <p>Current theme: {theme}</p>
                  <button onClick={() => setTheme("dark")}>Dark Mode</button>
              </div>
          )
      }

• 👉 Use when you need simple global state sharing without extra libraries.

⚡ Redux Toolkit

• ✅ What it is:
  • A state management library built on top of Redux.
  • Solves issues like boilerplate, immutability and complex reducers.
  • Best for large apps with complex state logic (API data, caching, user flows).
• ✅ How it works:
  • Create a store using configStore.
  • Create slices (createSlice) with reducers.
  • Use useSelector to read and useDispatch to update state.
• Example:

    // Import
    import {createSlice, configStore} from '@reduxjs/toolkit';
    import {useSelector, useDispatch, Provider} from 'react-redux'

    const themeSlice = createSlice({
        name: 'theme',
        initialState: {value: 'light'},
        reducers: {
            setDark: (state) => {state.value = 'dark' },
            setLight: (state) => {state.value = 'light' }
        }
    })

    const store = configStore({reducer: {theme: themeSlice.reducers}});

    const App = () => {
        return (
            <Provider store={store}>
                <Child/>
            </Provider>
        )
    }

    const Child = () => {
        const dispatch = useDispatch()
        const theme = useSelector((state)=> state.theme.value)
        return (
            <>
                <p>Theme: {theme}</p>
                <button onClick={()=> {dispatch(themeSlice.actions.setDark())}}>Dark Mode</button>
            </>
        )
    }

• 👉 Use when your app has complex state, many components depending on the same data, or you need predictable state debugging (Redux DevTools).

⚖️ Quick Comparison

Feature	Context API	Redux Toolkit
Built-in or external?	✅ Built into React	❌ External library
Boilerplate	Low	Medium (simplified by RTK)
Debugging tools	❌ None	✅ Redux DevTools
Async handling (API)	❌ Manual	✅ Built-in with createAsyncThunk
Best for	Small/medium apps, simple global state	Large/complex apps, scalable state mgmt

🧠 Interview One-liner

“I use Context API for small-scale state like theme or auth. For large apps with complex logic I prefer Redux toolkit because it gives structure, middleware and DevTools for debugging.”

⚡ Context API vs Redux Toolkit – Interview Scenarios

• Q1: Your app only needs to share a logged-in user’s info (name, email, role) across a few components. Which would you use?

  • 👉 Answer: Context API.
  • Because it’s lightweight, built-in, and enough for small state like auth or theme. Redux Toolkit would be overkill.

• Q2: You’re building an e-commerce app with cart, products, filters, orders, and wishlists. Data updates frequently and many components depend on it. Which do you use?

  • 👉 Answer: Redux Toolkit.
  • Because multiple components need the same state, updates are frequent, and you want debugging tools like Redux DevTools.

• Q3: You need to manage a dark/light theme toggle across the app. Which do you use?

  • 👉 Answer: Context API.
  • Simple global state → Context API is perfect.

• Q4: Your app fetches data from APIs (e.g., product list, user details) and you want to handle loading, success, and error states. Which do you use?

  • 👉 Answer: Redux Toolkit.
  • Because createAsyncThunk + slices make API state management clean and predictable.

• Q5: Your app has only 2–3 global states, but you want time-travel debugging to track how state changed over time. Which do you use?

  • 👉 Answer: Redux Toolkit.
  • Redux DevTools allow you to inspect, replay, and debug state changes.

• Q6: You are working in a team project where multiple developers need consistent state structure and maintainability. Which do you use?

  • 👉 Answer: Redux Toolkit.
  • Because it enforces structured state management and reduces bugs.

⚡ Quick Rule of Thumb

• ✅ Use Context API for → Auth state, theme toggles, language, or when state is small and simple.
• ✅ Use Redux Toolkit for → Large apps, async API data, debugging, and team projects.

🧠 Interview Trick Question

• Q: “Can Context API completely replace Redux?”
  • 👉 Answer: “Not really. Context API only solves prop drilling. It doesn’t provide middleware, async handling, or debugging tools like Redux Toolkit. For small state → Context is fine, but for scalable apps → Redux Toolkit is better.”