Exploring the Major Changes in Redux Toolkit 2.0 and React-Redux 9.0

Anton Ioffe - January 7th 2024 - 9 minutes read

As the redux saga continues to unfold, the latest iterations of Redux Toolkit and React-Redux present a groundbreaking evolution of state management paradigms in the JavaScript ecosystem. In this comprehensive deep-dive, we'll unravel the sophisticated enhancements introduced in Redux Toolkit 2.0 and React-Redux 9.0, anticipating the transformative impacts these changes bring to the cutting edge of React development. From the refined TypeScript support forging stronger type-safe fortifications, to the nuanced performance tuning capable of harnessing the full potential of React 18's concurrent features, we invite you on an exploratory journey scrutinizing the implications for your codebases and workflows. Whether seeking to finesse your application architecture or prevent common missteps during migration, our insights promise to arm you with the strategies necessary to navigate this redux renaissance.

Unpacking Redux Toolkit 2.0: The Major Shifts

Redux Toolkit 2.0 ushers in a pivotal transformation in state management practices for Javascript developers. One of the cornerstone changes is the revamped TypeScript support. The Redux core 5.0 renaissance comes in the form of a TypeScript rewrite, which beckons developers into an era of enhanced type safety. This rewrite ensures better compile-time error detection and a more robust design but requires teams to carefully adjust their type annotations to align with the new type definitions. It's paramount to perform thorough type checks across your application to harness this leap in static typing fully.

The middleware API has undergone a streamlining process, carving out a clearer and more concise approach to integrating middlewares. The introduce of the configureStore API is a declarative stride away from the now-deprecated createStore. This shift is more than a superficial renaming; it encapsulates a considerable architectural evolution where configureStore comes pre-configured with best practices and simplifies the process of setting up the store with middlewares like redux-thunk or redux-saga. The new API encapsulates complexity and exposes a much tidier interface to the developer, reducing boilerplate and improving development experience.

With the combineSlices API, Redux Toolkit 2.0 facilitates more dynamic code-splitting practices, easing the incremental loading of state in large-scale applications. The ability to inject slice reducers dynamically is a nod to the need for applications to be modular and performance-sensitive. This development strives to align Redux more closely with real-world use cases where loading efficiency and incremental state management are key concerns.

The enforced conventions introduced in Redux Toolkit 2.0 are not just a gentle nudge but a bold push toward more scalable and maintainable codebases. The insistence on string action types, for instance, is a type safety enhancement that eradicates a class of common bugs. These conventions encourage developers to adhere to patterns that not only preserve the runtime behavior but also augment the maintainability and scalability of applications as they grow and evolve.

In embracing these shifts, developers are called upon to steer away from createStore to the configureStore approach, embracing a more modern and feature-rich setup that is in congruence with Redux Toolkit 2.0's ethos. This transition is intertwined with adopting an architectural mindset that favors encapsulation, type safety, and modularity—cornerstones of the new Redux landscape. As Redux Toolkit matures with its 2.0 release, the explicit design choices and enforced conventions are molding state management into a more predictable and structured paradigm, elevating the quality and consistency of Redux-based applications.

React-Redux 9.0: Embracing Concurrent Rendering in React 18

React-Redux 9.0 is meticulously tailored to capitalize on the enhancements in React 18, particularly concurrent rendering capabilities. The hooks API has been meticulously refined, with useSelector now safeguarding against state inconsistencies during concurrent updates. Essentially, useSelector ensures that components receive the latest state reflective of React's rendering queue, therefore reducing instances of stale or inconsistent state during rapid state changes.

Key to its architectural refinement, React-Redux has shed the legacy context API in favor of createContext, interfacing more cleanly with concurrent mechanisms in React 18. This shift decisively addresses the "tearing" issue where different parts of the app might see different state values in a single render. With the connect function retooled for concurrent rendering, connected components can trigger independent renderings that leverage React 18's queuing and batching capabilities for high-performance state management.

Yet, careful attention must be paid when adapting to concurrent rendering, as developers must now consider the scheduling and prioritization of state updates. The holistic adoption of concurrent features like useTransition in Redux-driven components might involve patterns that separate non-urgent state updates from those that are critical to immediate user interactions. For example:

import { useSelector, useDispatch } from 'react-redux';
import { useTransition } from 'react';
import { updateValue } from './valueSlice';

function MyComponent() {
  const [isPending, startTransition] = useTransition();
  const value = useSelector(selectSomeValue);
  const dispatch = useDispatch();

  function handleUpdate(newValue) {
    startTransition(() => {

  // Component rendering logic with appropriate handling of isPending state

Adapting such techniques ensures that developers reap the concurrency benefits without undermining the responsiveness or stability of the application.

In harmony with React 18, React-Redux 9.0 empowers developers to navigate the complexities of contemporary state management. While enabling more responsive and dynamic interfaces, this congruence anticipates the user demand for swift interactions and lays the groundwork for robust applications that perform seamlessly across a spectrum of user conditions. Through thoughtful integration, developers are armed with the means to maneuver through intricate state management landscapes with poise.

Codebase Refinement and Developer Experience

Redux Toolkit 2.0 has fundamentally redefined code quality and developer experience by streamlining store configuration. The reimagined configureStore method adeptly consolidates middleware and devtools in a coherent API, cutting down on redundant boilerplate. Here's an enhanced store configuration that leverages the improved dev tools integration:

import { configureStore } from '@reduxjs/toolkit';
import rootReducer from './rootReducer';

const store = configureStore({
  reducer: rootReducer,
  middleware: (getDefaultMiddleware) =>
  devTools: process.env.NODE_ENV !== 'production',

The inclusion of devTools right in the configuration illustrates this ease, with developers no longer needing to manually integrate additional tools for debugging. Enhanced functionalities like live editing of code and time-travel debugging are now part of the debugging process, fostering an intuitive and integrated development workflow.

The createSlice function in Redux Toolkit 2.0 has been ingeniously redesigned, enabling developers to define actions and reducers in a unified structure. Utilizing Immer’s library under the hood, createSlice allows us to write cleaner, mutation-like reducer logic safely. Here's a revised createSlice example showcasing this best practice:

import { createSlice } from '@reduxjs/toolkit';

export const counterSlice = createSlice({
  name: 'counter',
  initialState: { value: 0 },
  reducers: {
    increment(state) {
      // It's safe to do this because createSlice uses Immer
      state.value += 1;
    decrement(state) {
      state.value -= 1;

This approach is not only syntactically simpler, but it also guarantees safe state updates, enhancing code readability and maintainability without having to manage complex immutable update logic.

In a forward-looking move, Redux Toolkit 2.0 has further integrated dev tools functionalities. Now, developers can effortlessly inspect the minutiae of their state with advanced features like action traceability and state diff logs, pinpointing precisely how each action transforms state across the application. The sophistication of dev tools is now baked into every action dispatch, making the intricate state transitions of Redux transparent and navigable.

Paring down boilerplate extends into asynchronous operations with createAsyncThunk. This function provides a streamlined way to handle async logic within Redux without cumbersome setup. Here's an improved createAsyncThunk example, complete with error handling:

import { createAsyncThunk } from '@reduxjs/toolkit';

export const fetchData = createAsyncThunk(
  async (arg, { rejectWithValue }) => {
    try {
      const response = await fetch(arg);
      if (!response.ok) throw new Error('Network response was not ok.');
      return response.json();
    } catch (error) {
      // Handling errors in createAsyncThunk's payload creator
      return rejectWithValue(error.message);

In this example, error handling is meticulously incorporated, allowing actions to handle both success and failure scenarios gracefully, which aligns well with real-world development practices. This mindful approach facilitates a predictable state management experience, ensuring that Redux not only meets the rigor of modern web development but sets a new standard of excellence.

Common Mistakes and Best Practices in Adoption

One prevalent pitfall when adopting Redux Toolkit 2.0 and React-Redux 9.0 revolves around state mutation. Despite the convenience of the included Immer library in createSlice, some developers erroneously attempt to mutate the state directly outside of reducers. This antipattern breaks the core principle of Redux’s immutable state management. For example:

// Incorrect: Directly mutating state

// Correct: Utilizing Immer to handle immutability behind the scenes
state.items = [...state.items, action.payload];

Another common oversight relates to selector usage. createSelector from Redux Toolkit offers memoization, yet developers might forget to use it, leading to unnecessary recalculations when deriving data from the state. Worse, they may create new selectors inside a component, violating the memoization principle:

// Incorrect: New selector created on every render
const totalPrice = useSelector(state => state.cart.items.reduce((total, item) => total + item.price, 0));

// Correct: Memorized selector defined outside the component
const selectTotalPrice = createSelector(
    [state => state.cart.items],
    items => items.reduce((total, item) => total + item.price, 0)
const totalPrice = useSelector(selectTotalPrice);

Redundant renders often stem from misuse of useSelector. If the selector returns a new object or array each time, it will cause the component to re-render needlessly. The solution is to ensure selectors return consistent references whenever possible:

// Incorrect: Selector returns a new object every time
const userSettings = useSelector(state => ({ theme: state.settings.theme }));

// Correct: Selector returns the same reference if the theme hasn't changed
const selectTheme = createSelector(
    state => state.settings.theme,
    theme => ({ theme })
const userSettings = useSelector(selectTheme);

Envisaging a seamless migration, developers should embrace feature-centric structuring of state. Bypassing this strategy may lead to tangled state relationships and code clarity issues. Refrain from organizing state slices purely on data type and consider how they are used by the UI:

// Considered antipattern: Slicing state strictly by data types
// Proposed best practice: Slices aligned with features/UI components

Avoid the temptation to retain legacy approaches out of comfort. Failing to adopt new patterns such as batch from React-Redux for dispatching multiple actions or leveraging createAsyncThunk for async flows forfeits the enhancements in Redux Toolkit 2.0 and React-Redux 9.0, leaving applications with outdated paradigms:

// Incorrect: Dispatching actions sequentially causing multiple renders

// Correct: Batching actions to render once
import { batch } from 'react-redux';
batch(() => {

In conclusion, when adopting the Redux Toolkit 2.0 and React-Redux 9.0, developers must stay vigilant against outdated practices and embrace new conventions, ensuring a transition that fully capitalizes on the libraries’ potential for a more maintainable and performance-optimized codebase.

Performance Patterns and Optimization Strategies

Recognizing the importance of optimizing state management for performance, Redux Toolkit 2.0 and React-Redux 9.0 bring innovative approaches such as selector factories. The entityAdapter.getSelectors() method can be enhanced with custom selectors for memoization, aiming to streamline component re-renders. Here's an improved example of how selectors can be used with the Redux Toolkit's createEntityAdapter, providing memoization for derived data:

import { createEntityAdapter, createSelector } from '@reduxjs/toolkit';

const usersAdapter = createEntityAdapter();
const { selectAll } = usersAdapter.getSelectors(state => state.users);

const selectUserFriends = createSelector(
    [selectAll, (state, userId) => userId],
    (users, userId) => users.filter(user => user.friends.includes(userId))

// Usage within a component
const FriendsList = ({ userId }) => {
    const friends = useSelector(state => selectUserFriends(state, userId));
    // Component logic here

By correctly memoizing selectors that compute derived data, such as the list of friends for a particular user, components only re-render when the relevant data changes, reducing the unnecessary workload on the system.

Automatic batching in React-Redux 9.0 enhances performance notably by grouping state updates. In scenarios where multiple updates may occur in response to an action, batch() from React-Redux can be used to consolidate re-renders into one:

import { batch, useDispatch } from 'react-redux';
import { updateProfile, loadMessages } from './actions';

const useUpdateProfileAndLoadMessages = () => {
    const dispatch = useDispatch();

    return (profile, userId) => {
        batch(() => {

This code elegantly illustrates how actions can be batched to minimize re-rendering and create a more efficient and fluid application experience across different domains.

In Redux Toolkit 2.0, middleware serves as a pivotal point for adjusting performance. Custom middleware can be crafted for performance tuning such as action throttling. The following example incorporates a straightforward throttling logic:

import { configureStore } from '@reduxjs/toolkit';
import { throttle } from 'lodash';

const performanceMiddleware = store => next => throttle(action => {
    // Throttling logic here can prevent this action from being dispatched too frequently
    return next(action);
}, 1000);

const store = configureStore({
    middleware: getDefaultMiddleware =>

In this snippet, the throttle function is utilized to limit the number of times an action can be dispatched, avoiding excessive state updates and thereby enhancing application performance. Developers should ensure such middleware adds performance gains without causing bottlenecks.

Memoization and intelligent selector usage are fundamental for complex Redux applications. Selector factories and batch updates significantly cut down unnecessary re-renders, while middleware must be wielded tactically to improve performance. Regular reviews of application performance are essential, and developers should thoughtfully employ these tools to achieve an equilibrium between responsive interfaces and efficient state management.


In the article "Exploring the Major Changes in Redux Toolkit 2.0 and React-Redux 9.0", the author discusses the significant advancements in Redux Toolkit and React-Redux that have revolutionized state management in JavaScript. The author highlights key shifts in Redux Toolkit 2.0, such as improved TypeScript support, streamlined middleware integration, and the introduction of combineSlices API for dynamic code-splitting. The article also explores the compatibility between React-Redux 9.0 and React 18's concurrent rendering capabilities, emphasizing the importance of handling state inconsistencies and prioritizing state updates. The author provides insights on codebase refinement, developer experience, common mistakes, performance optimization strategies, and challenging tasks that prompt readers to actively implement the discussed techniques in their projects.

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