Utilizing Redux Toolkit 2.0: Advanced Features and Upgrades

Anton Ioffe - January 6th 2024 - 10 minutes read

As they navigate the ever-evolving landscape of web development, seasoned JavaScript engineers recognize the pivotal role of efficient state management in crafting scalable applications. Redux Toolkit 2.0 emerges as a game-changer, bestowing upon developers a suite of advanced features ingeniously designed to enhance performance, streamline workflows, and elevate the developer experience to new heights. This article ventures into the latest upgrades of Redux Toolkit, offering an expert's perspective on the architectural leaps in store configuration, refined slice mechanics, innovative data fetching paradigms, and state-of-the-art selector techniques. Prepare to immerse yourself in an enlightening journey through Redux Toolkit 2.0 that promises not only to refine your current practices but also to optimally position your projects for the future's promising frontier.

Evolution of Redux Toolkit: The 2.0 Paradigm Shift

Redux Toolkit (RTK) 2.0 heralds a new era of state management with substantial refinements aimed at improving the experience for developers and promoting best practices. One of the most noteworthy alterations is the TypeScript rewrite of the Redux core. This change, which was first proposed in 2019 and later integrated into the codebase, has finally been brought to light with the release of RTK 2.0. This TypeScript conversion presents a double-edged sword: on one hand, it guarantees a strictly typed environment conducive to fewer runtime errors and improved code auto-completion. On the other hand, it could potentially instigate type-related issues for existing projects during migration. However, the long-term benefits of stronger type safety and enhanced developer tooling arguably justify the necessary adjustments.

The deprecation of createStore in favor of configureStore delivers a more robust and intuitive API for building stores. The old createStore approach often led to verbose and repetitive configurations, particularly when applying middleware or composing enhancers. The revamped configureStore API abstracts this complexity, inferring middleware from the supplied reducers and automatically setting up the Redux DevTools extension. Consider the typical pre-2.0 configuration:

import { createStore, applyMiddleware } from 'redux';
import rootReducer from './reducers';

const store = createStore(
  applyMiddleware(/*...middleware list...*/)

Under the 2.0 paradigm, setting up the store becomes more streamlined and eliminates the need to manually apply middleware:

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

const store = configureStore({
  reducer: rootReducer,

This refinement significantly reduces boilerplate and improves readability, making it easier for developers to reason about the store configuration process.

Additionally, performance receives subtle yet meaningful enhancements due to tighter internal code alignment with modern JavaScript capabilities. This alignment serves to trim unnecessary re-rendering and improve memory usage, particularly in large-scale applications where every optimization has a tangible impact. The implications for existing applications are promising, potentially offering more responsive interfaces with less overhead.

In terms of complexity, the update takes a leap towards simplification. Developers accustomed to the verbose patterns of original Redux will find RTK 2.0 encapsulates many best practices into default behaviors, thereby lowering the barrier to entry and allowing developers to focus more on business logic rather than the intricacies of state management structures. One could argue that the switch may obscure some of the internals pivotal to Redux’s predictable state container philosophy, but the trade-off for ergonomics and reduced error-proneness suggests a net positive impact.

The new Redux Toolkit version endeavors to encourage the evolution of Redux applications into cleaner, more maintainable, and scalable systems. The adjustments made in 2.0 may present a learning curve or introduce the necessity for refactoring efforts, but it is clear that the Redux team prioritized long-term sustainability and developer satisfaction. Significantly, these changes set forth a question for seasoned developers to ponder: how can we leverage the newfound capabilities of RTK 2.0 to not just maintain the status quo, but innovate further in our approach to state management?

Enhanced Slice and Middleware Mechanics

Redux Toolkit 2.0 introduces combineSlices, a radical enhancement that allows developers to dynamically inject slice reducers at runtime. This capability facilitates lazy-loading of reducers which is a boon for performance in large-scale applications. combineSlices not only simplifies the combination of slices by exploiting the slice.name field but also augments the combined reducer with an .inject() method, enabling modular and on-demand state shape extensions. This contrasts with prior versions where you would have to manually combine reducers and delegate dynamic requirements to application logic, potentially making state management cumbersome.

const usersSlice = createSlice({ name: 'users', /* slice content */ });
const postsSlice = createSlice({ name: 'posts', /* slice content */ });

const reducer = combineSlices(usersSlice, postsSlice);
// At a later time, for example during a code-splitting route load
reducer.inject(createSlice({ name: 'comments', /* slice content */ }));

createSlice takes a new turn with the addition of a selectors field, offering a convenient alternative to defining selectors separately and importing them wherever necessary. Previously, developers would create selectors using external functions, which while decoupled, demanded repetitive boilerplate for accessing slice state. Now, by defining selectors inline, one can capitalize on colocation and reduce unnecessary re-definition of selectors across the application. This direct association between the slice and its selectors streamlines state access and improves readability without sacrificing reusability.

const slice = createSlice({
    name: 'counter',
    initialState: 42,
    reducers: { /* reducers here */ },
    selectors: {
        selectCount: state => state
// Accessing the selector
const count = useSelector(slice.selectors.selectCount);

The integration of thunks within createSlice via createSlice.reducers callback syntax is a significant improvement towards a more declarative approach to async logic in slices. You can now eschew writing thunks separately, avoiding action type prefixing and excess boilerplate for handling asynchronous actions through extraReducers. By contrast, with the new callback syntax, thunks nest neatly within the slice, codifying async flows inline with the rest of the slice logic, optimizing code navigability and concentricity, while preserving efficiency.

const slice = createSlice({
    name: 'userData',
    initialState: { loading: false, data: null },
    reducers: (builder) => ({
        fetchUserById: builder.thunk(async (userId, { dispatch, getState }) => {
            // Async logic here

The advent of "dynamic middleware" middleware solidifies Redux Toolkit as a flexible state management tool suitable for intricate use cases such as code splitting. The ability to insert and remove middleware at runtime ensures applications can adapt to changing runtime requirements, possibly aiding in the reduction of the initial bundle size. This issue was previously managed with workarounds, but now, Redux Toolkit offers a first-class API to handle this complexity efficiently, marking a key development for modularity in Redux applications.

const { middleware: dynamicMiddleware } = createDynamicMiddleware();
const store = configureStore({
    reducer: rootReducer,
    middleware: (getDefaultMiddleware) => getDefaultMiddleware().concat(dynamicMiddleware),

// Dynamically add middleware later

The new updates, while fostering performance and customization, carry the risk of becoming intricately entangled with application logic if overused. Developers should weigh the impact of increased modularity against potential complications in understanding the flow of state and actions through the system. Does the convenience and power introduced by Redux Toolkit 2.0's dynamic features warrant changing established project structures, or should these be adopted gradually, in areas where high impact is assured?

RTK Query and Modern Data Fetching Patterns

Redux Toolkit 2.0's RTK Query introduces a fundamental revamp in the way we handle data fetching and state management for asynchronous operations in React. A critical upgrade in this release is the refinements in reactHooksModule configurations. In previous versions, configuring custom hooks like useSelector or useDispatch for alternative Redux store contexts was somewhat error-prone. Developers could inadvertently omit useStore when providing custom hooks, breaking the expected behavior. The new configuration pattern requires all three hooks to be provided under a single hooks object, mitigating the risk of such errors. For instance, customizing hooks now involves a straightforward structure:

const customHooks = reactHooksModule({
  hooks: {
    useDispatch: createDispatchHook(MyContext),
    useSelector: createSelectorHook(MyContext),
    useStore: createStoreHook(MyContext),

Notably, this modification emphasizes the importance of a cohesive hook ecosystem, thus reducing complexity and improving modularity. Yet, it may introduce a temporary challenge as developers adapt their codebases to accommodate this uniform approach.

Alongside hooks configuration, RTK Query optimizes the performance of data fetching. One subtle but impactful change is the optimization of cache entry updates to reduce unnecessary Redux state syncs. Previously, every RTK Query cache update triggered a state sync, potentially leading to performance bottlenecks. However, the new version strategically syncs these values, significantly improving performance, particularly for applications with heavy data transactions.

Error handling has also been enhanced, with RTK adopting a strategy similar to React's for production builds—extracting error message strings out of the bundle. This change trims down the production bundle size, which can lead to faster load times for end-users. Nonetheless, it's crucial to ensure efficient error tracking and logging mechanisms are in place, as these optimizations might obscure debug information that was previously more accessible in production builds.

On the downside, these refinements encourage a heavier reliance on convention over configuration, potentially concealing low-level processes and making it harder for developers who prefer having fine-grained control over their application's inner workings.

RTK Query's enhancements in Redux Toolkit 2.0 reflect an ongoing effort to address the nuances of modern data fetching. By focusing on performance optimizations, improved error handling, and a more robust hooks configuration, RTK Query enables developers to manage asynchronous state with greater efficiency and less overhead. But as the landscape of web development persists in its rapid evolution, the debate over the balance between abstraction and control continues. How should developers tread the line between adopting these higher-level tools and maintaining a clear understanding of their application's state management mechanisms?

Migrating to Enhanced Selectors and Memoization Techniques

In the latest Redux Toolkit, createSelector has been supercharged by eschewing its original defaultMemoize function for weakMapMemoize as its default memoization strategy. The change reflects a nuanced pivot towards a more sophisticated caching technique that leverages WeakMaps to maintain references without impeding garbage collection. The benefits are clear: improved cache management and reduced concerns about cache size for selectors with dynamic and changing arguments. However, this approach is limited by the reliance on reference equality, which precludes fine-tuning for cases where deep comparison is necessary. For developers requiring tight control over equality checks, the flexibility is still present; createSelector can be customized to use the now-renamed lruMemoize, allowing for a custom equality function to be provided:

const createSelectorWithLRUMemoize = createSelector(
        memoize: lruMemoize,
        memoizeOptions: { equalityCheck: deepEqualCheck }

With these changes come new development-mode checks in createSelector aimed at avoiding common pitfalls that affect memoization efficacy. While incredibly helpful in pinpointing inefficacies, there's a trade-off in readability when selectors become cluttered with additional checks and configurations. Developers transitioning to the updated Redux Toolkit must remain vigilant to preserve the clarity of their selectors. For instance, input selectors that inadvertently return different objects will sabotage memoization:

// Problematic in terms of memoization
const unstableSelector = createSelector(
    (state) => ({...state.someData}),
    (data) => data
// Corrected for stable references
const stableSelector = createSelector(
    state => state.someData,
    someData => someData

Another migration step involves adapting to the removal of ParametricSelector types. This change simplifies the types ecosystem around selectors, reducing them to Selector and OutputSelector. Developers now will use these streamlined types to articulate the input-output relationships within selectors, promoting uniformity and possibly easing the mental mapping of type relations, albeit with a slight reduction in specificity in certain use cases.

Bringing to life robust selectors with Redux Toolkit 2.0 means acknowledging and addressing the deprecated patterns while embracing the advancements. It is not merely about code alterations but adopting a mindset that balances performance gains against the potential increase in complexity. The aim is to craft selectors that are not only efficient but maintainable; this entails leveraging the provided tools to catch anti-patterns early and effectively utilizing the memoization options in alignment with the application's needs.

On a closing note, as developers execute these migrations, a thoughtful examination of existing selector patterns is due. Which selectors are prone to recalculations due to unstable references? How might the restructured memoization techniques affect state selection performance? When should developers prefer weakMapMemoize over lruMemoize or vice versa, and how does this choice reflect on the overall application architecture? These contemplations underscore the migration process, urging developers to refine selectors not just for compliance with the new toolkit, but for the sustained quality and performance of their Redux-based applications.

Future-Proofing Applications with Redux Toolkit 2.0

With the launch of Redux Toolkit 2.0, developers have been provided with tools to future-proof their applications. A notable advancement is the conceptualization of custom slice reducer creators, which offer a flexible path for managing application state. This pioneering feature lays groundwork for the seamless incorporation of emerging techniques, such as those we can expect with the forthcoming RTK Query in version 3.0.

Consider the following tailored cartSlice reducer designed for an ecommerce platform, thoughtfully structured to embrace future updates:

const cartSlice = createSlice({
  name: 'cart',
  initialState: { items: [], total: 0 },
  reducers: {
    addItem(state, action) {
    removeItem(state, action) {
      state.items = state.items.filter(item => item.id !== action.payload.id);
  // Anticipate future needs for new patterns like RTK Query associations
  extraReducers(builder) {
    // Placeholder for integration with additional RTK Query actions or other async patterns

Selector enhancements with Redux Toolkit are another element to stay ahead with. By judiciously employing selector factories, application state will be managed efficiently, setting the groundwork for RTK's subsequent versions. An example selector construction with RTK 2.0 might look like this:

const selectItems = state => state.cart.items;
const selectTotal = createSelector(
  items => items.reduce((total, item) => total + item.price, 0)

Crafting RTK 2.0-compliant code means adhering to the principles of modern JavaScript, focusing on reusable and modular structures. Encapsulate logical operations within slices and selectors, prepping for a transition to RTK Query or other progressive state management methods.

Deliberate on the following: Will leveraging RTK 2.0's advanced utilities integrate smoothly within your current architecture? Are your strategies setting a stage where integration with RTK Query and the promised advancements in version 3.0 is streamlined? How might custom reducer creators and selector factories impinge on system performance?

In adopting RTK 2.0's advanced features, it is crucial for developers to ensure that their codebases uphold cleanliness, modular construction, and performance standards. Ongoing assessments of how new features interact with these core tenets will provide a solid foundation for future enhancements, allowing for the swift and effective adoption of forthcoming capabilities.


Redux Toolkit 2.0 brings advanced features and upgrades to JavaScript developers in modern web development. The article highlights the improvements in Redux Toolkit, including a TypeScript rewrite, a more robust store API, performance enhancements, and simplified state management. It also covers the enhanced slice and middleware mechanics, the modern data fetching patterns with RTK Query, and the migration to enhanced selectors and memoization techniques. The article concludes by emphasizing the importance of future-proofing applications with Redux Toolkit 2.0 and encourages developers to think about how they can leverage the new features to optimize their projects. A challenging task for readers would be to analyze their existing Redux applications and consider how they can incorporate the advanced features of Redux Toolkit 2.0, such as the new store configuration, dynamic reducers, or memoized selectors, to improve performance and maintainability.

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