Q273- Difference between Redux-Thunk and Redux-Saga

Both Redux-Thunk and Redux-Saga are middleware used to handle asynchronous logic (API calls, timers, side effects) in Redux — but they work in completely different ways.

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✅ 1. Redux-Thunk (Simple + Promise-based)

✔ How it works:

• Allows returning functions from actions
• These functions can run async code (API calls)
• You manually dispatch actions after async calls

✔ Best for:

• Small to medium apps
• Simple async flows
• Few API calls

✔ Example:

export const fetchUsers = () => async (dispatch) => {
  dispatch({ type: "LOADING" });

  const res = await fetch("/users");
  const data = await res.json();

  dispatch({ type: "SUCCESS", payload: data });
};

Summary:

• Promise/async-await based
• Easy to understand
• Less boilerplate
• Not good for complex flows

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✅ 2. Redux-Saga (Powerful + Generator-based)

✔ How it works:

• Uses ES6 generator functions (function*)
• Side effects are managed as sagas
• You can pause, resume, cancel, retry async tasks
• Supports complex async flows easily

✔ Best for:

• Large applications
• Complex workflows
• Background tasks
• Multiple dependent API calls
• Real-time updates
• WebSocket handling

✔ Example:

function* fetchUsers() {
  try {
    yield put({ type: "LOADING" });

    const data = yield call(api.getUsers);

    yield put({ type: "SUCCESS", payload: data });
  } catch (error) {
    yield put({ type: "ERROR", error });
  }
}

Summary:

• Generator-based
• Allows cancelling, debouncing, throttling
• Best for advanced async logic

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🔥 Key Differences

Feature	Redux-Thunk	Redux-Saga
Approach	Async functions (Promises)	Generator functions
Complexity	Simple	Complex
Best for	Small–medium apps	Large scalable apps
Flow control	Limited	Advanced: cancel, retry, parallel tasks
API calls	Manual	Structured with effects (call, put)
Side effects	Handled inside thunks	Centralized sagas
Learning curve	Easy	Hard

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⭐ Which One Should You Use?

✔ Use Redux-Thunk when:

• Your app has simple API calls
• You want minimal configuration
• You prefer async/await style

✔ Use Redux-Saga when:

• You have advanced async workflows
• Need cancellation or retry logic
• App is large or enterprise-level
• Working with WebSockets or background tasks

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🎯 Short Interview Answer

Redux-Thunk is a simple, promise-based middleware that allows async functions inside actions. It's ideal for small apps.
Redux-Saga uses generator functions to handle complex async logic like cancellation, retries, debounce, and parallel tasks — ideal for large applications.