Single Source of Truth

Single Source of Truth sits at the heart of redux core concepts in Redux. This guide walks through the concept step by step, with examples, a cheatsheet, and common mistakes to avoid.

Single Source of Truth Overview

Single Source of Truth is something you will reach for often in Redux. It keeps your workflow predictable and makes your intent obvious to reviewers and teammates.

When you learn single source of truth properly, you avoid the guesswork that leads to mistakes and rework. The example below shows the shape you will use in most real Redux projects.

import { configureStore } from '@reduxjs/toolkit';
import { Provider } from 'react-redux';

const store = configureStore({ reducer: rootReducer });

function App() {
  return (
    <Provider store={store}>
      <Root />
    </Provider>
  );
}

A Provider makes the single Redux store available to every component in the tree.

Single Source of Truth Example

const slice = createSlice({ name, initialState, reducers });
const store = configureStore({ reducer: { key: slice.reducer } });
// dispatch(slice.actions.something())

Start from a minimal Single Source of Truth example and grow it only as needed.
Keep things explicit so Single Source of Truth behaves the same for everyone on the team.
Name things clearly so teammates understand your Single Source of Truth at a glance.
Verify Single Source of Truth works as expected before relying on it in important work.

Redux Cheatsheet

Quick Redux Toolkit reference related to single source of truth.

Concept	Example	Purpose
Store	`configureStore({ reducer })`	Hold app state
Slice	`createSlice({ name, reducers })`	State + actions together
Read state	`useSelector((s) => s.x)`	Get data in components
Dispatch	`useDispatch()`	Send actions
Async	`createAsyncThunk(...)`	Handle side effects
Data fetching	`createApi(...)`	RTK Query endpoints
Derived data	`createSelector(...)`	Memoized computations

How Single Source of Truth Works in Redux

Single Source of Truth follows Redux's predictable data flow: components dispatch actions, reducers compute the next state from the previous state and the action, and subscribed components re-render.

A Provider makes the single Redux store available to every component in the tree.

State lives in a single, read-only store.
Actions are the only way to describe a change.
Reducers are pure functions that return the next state.
Redux Toolkit removes most boilerplate with slices and thunks.

Practical Guidance for Single Source of Truth

In modern apps, single source of truth should use Redux Toolkit rather than hand-written Redux. Keep state minimal, colocate logic in slices, and use RTK Query for server data.

Concern	Recommendation
Boilerplate	Use Redux Toolkit (createSlice)
Server data	Prefer RTK Query over manual thunks
Performance	Memoize selectors with createSelector
Types	Use typed useAppSelector/useAppDispatch hooks

Common Mistakes

Skipping edge cases and error handling when using single source of truth.
Not verifying the result of single source of truth before moving on.
Over-complicating single source of truth before you actually need the extra flexibility.
Ignoring documentation, which makes single source of truth hard for the next person to follow.

Key Takeaways

Single Source of Truth is a core part of working effectively with Redux.
Start small and keep single source of truth focused on a single goal.
Apply consistent patterns so single source of truth scales across your project.
Practise and document single source of truth to keep your workflow maintainable.

Pro Tip

Practise single source of truth on a throwaway project first. It is far cheaper to learn Redux mistakes there than on important work.