React-Redux 9.0 and Redux v5.0.0: Synchronized Major Versions

Anton Ioffe - January 6th 2024 - 10 minutes read

In the rapidly evolving landscape of modern web development, staying abreast of the latest updates is vital for the seasoned developer. With the synchronized release of React-Redux 9.0 and Redux v5.0.0, our development ecosystem takes a harmonized leap forward, promising significant enhancements that will shape the way we manage state in React applications. This article delves into the concerted efforts of both libraries to streamline the developer experience, presenting a fusion of features and improvements that will not only demand your attention but also redefine best practices in your large-scale projects. Prepare to navigate through the synergized pillars of architecture, performance, and developer ergonomics, as we dissect each advancement and its implications on your craft, embellished with pragmatic insights and code wisdom tailored for the skilled artisan in you.

Synchronized Release Analysis

The synchronized release of React-Redux 9.0 alongside Redux v5.0.0 is a notable move that serves various strategic purposes in the wider context of front-end development. Foremost among these is the endeavor to align the versioning, thereby simplifying the upgrade process for developers. In doing so, the maintainers have streamlined the version dependency management, enabling an unambiguous reference point for compatibility between these often-co-used libraries. This move positions both libraries as mutually inclusive, making it clearer for developers to ascertain which versions are intended to work together without the need to sift through extensive release notes for compatibility insights.

From a development strategy vantage point, unifying major versions helps signal a consolidated upgrade path for large projects or enterprise-grade applications that rely on stability and predictability. Projects can now plan their update strategy with a clearer roadmap, given that both libraries will have been tested and designed to function together from the outset. While developers could previously face mixed results or unexpected behavior due to incompatible library versions, synchronous versioning addresses these concerns by bolstering the confidence that the shared major version number will ensure interoperability out-of-the-box.

Notably, synchronized versioning addresses the evolution of the ecosystem, particularly with concurrent features in React such as time-slicing and Suspense. Given the complexities these features introduce regarding synchronous external stores like Redux, having React-Redux in sync with Redux’s versioning promises a smoother adjustment as these new React capabilities become mainstream. This coordinated approach indicates a broader forward-looking strategy, taking into account not only current synergies between the libraries but also the anticipated future state of React development.

Digging deeper into the implications of concurrent features, the synched releases suggest a preference for maintaining consistency across the entire React tree. This is framed against the backdrop of potential issues like "tearing", where disparate parts of the application may receive different state values during a single render pass. Synchronized versions help circumvent such issues, as developers can rest assured that both libraries have been adapted to operate under these new concurrent conditions without introducing discrepancies within the state management flow.

However, it’s worth acknowledging that not all projects may immediately benefit from the synchronized release, especially those tightly coupled to third-party dependencies that may take longer to adapt to the newest versions. The move may prompt a re-evaluation of such dependencies, pushing towards a more deliberate composition of the projects’ library ecosystem. Developers are to be cognizant of the landscape surrounding their project's dependencies, ensuring that their auxiliary libraries are equally prepared for the concurrent updates to Redux and React-Redux.

Architectural and Feature Enhancements

In React-Redux 9.0, an emphasis on modularity has driven architectural changes. Most notably, React 18 is a requirement, enabling the Redux ecosystem to fully leverage the features offered by the latest React version. By embracing React's advancements like hooks and concurrent rendering, React-Redux has streamlined its internal implementation. The move away from legacy context to createContext for state sharing stands out as a milestone, improving the compatibility with React's more modern paradigms.

The introduction of enhanced hooks in version 7.1.0 has been further polished. The useSelector, useDispatch, and useStore hooks have become the standard for accessing Redux store's state and dispatch functionality within functional components. Their usage reinforces a shift towards functional programming in Redux applications, aligning with React's hook-centric approach. This hooks update underscores a pivot from the previously relied-on connect High Order Component (HOC) pattern, compelling developers to revisit their state management strategies with an eye for functional react patterns.

Redux v5.0.0 goes hand-in-hand with these changes, bringing about new capabilities with minimal disruption. One such advancement is the combineSlices API in Redux Toolkit 2.0. This innovation fosters code-splitting by allowing dynamic injection of slice reducers, which can be especially useful in large-scale applications where reducing the initial load time and incrementally loading state as needed enhances performance. By embracing this pattern, Redux now better accommodates the complexity and modularity demands of real-world web applications.

The combineSlices feature not only addresses performance optimization through code-splitting but also elevates code organization. By allowing developers to modularly couple action creators with their associated slice reducers, the Redux state's shape becomes more maintainable and easier to reason about. This clear separation of concerns carries implications for improved reusability and readability across the codebase, aiding in managing the inevitable scaling of state logic.

However, with these enhancements come potential pitfalls. Adapting to the new hooks and APIs requires a re-examination of common coding practices. For instance, over-reliance on connect can lead to missed opportunities for performance improvements with useSelector. Additionally, misunderstanding the combineSlices API may result in improperly managing code-splitting, thus negating its benefits. Developers should consider evaluating their current Redux implementation to ensure they are not only aligning with these enhancements but also avoiding such missteps. How will your existing Redux practices shift to accommodate the advanced hooks system? And in what ways can combineSlices aid your application's structure to leverage Redux's enhanced capabilities?

Breaking Changes and Migration Path

With the release of Redux Toolkit 2.0 and Redux core 5.0, the createStore function has been deprecated, marked by a visual strikethrough. Although createStore will remain usable for backward compatibility, teams are strongly encouraged to transition to configureStore from Redux Toolkit for future development. Those who wish to avoid the strikethrough notation can employ import { legacy_createStore as createStore } from 'redux' without affecting existing codebases. Transitioning to configureStore is not only about adhering to best practices but also about leveraging enhancements for improved development experiences.

The TypeScript rewrite accompanying Redux core 5.0 concentrates on enhancing type safety and maintaining runtime behavior compatibility. Developers should be aware that, despite efforts to ensure a smooth transition, there may be type discrepancies due to the translation from JavaScript to TypeScript. It is crucial for development teams to conduct comprehensive type checks across their applications and adjust their type annotations where necessary to resolve any discrepancies and take full advantage of the stronger type system.

Adjustments to middleware typings introduce a new requirement: both action and next parameters in middleware functions must now be explicitly typed, as they are considered unknown. This change is exemplified as follows:

const myMiddleware = store => next => action => {
  // Explicit type casting is necessary for 'action' and 'next'
  const typedAction = action as MyActionType;
  const typedNext = next as NextDispatcherType;
  // Middleware logic using typedAction and typedNext
  return typedNext(typedAction);

Developers must update their middleware to include explicit type assertions, aligning with the aim to mitigate type-related errors and streamline state management practices.

Moreover, configureStore now requires declaring middleware as a callback function instead of using object syntax, to promote functional programming patterns. This enhances modularity and paves the way for more dynamic middleware configurations. This can be implemented like so:

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

const store = configureStore({
  reducer: rootReducer,
  middleware: getDefaultMiddleware => getDefaultMiddleware().concat(myMiddleware),

Finally, Redux core 5.0 enforces that action.type values must be strings, consistent with previous versions, to eliminate the use of non-string action types such as symbols. This enforcement tightens the contract for action types across the Redux ecosystem. It's a best practice to ensure actions are standardized, facilitating maintainability and predictability within the app state. Legacy implementations employing non-string action types will need to align with this standard to avoid runtime errors:

// Correct action type definition
  type: 'MY_ACTION_TYPE',
  payload: {...}

This stringent approach underscores Redux's commitment to a unified, best-practice-driven environment. It is imperative for developers to review their action creators and adjust any unconventional action types to comply with this requirement.

Performance and Developer Experience Upgrades

The introduction of automatic batching in the Redux middleware brought a significant leap in performance by grouping multiple state updates into a single re-render. This improvement, which takes cues from React 18's new rendering strategy, capitalized on the unstable_batchedUpdates() API provided by React. The implementation can lead to substantial gains especially in scenarios with multiple dispatches occurring in rapid succession. For instance, complex user interactions that trigger a cascade of actions can now be handled more efficiently, preventing unnecessary re-renders and thus saving valuable computation resources.

Alongside batching, the updated entityAdapter.getSelectors() in Redux Toolkit (RTK) introduces the concept of selector factories. By allowing developers to pass a createSelector method as part of an options object, greater control over the memoization of selectors is possible. This not only provides flexibility in terms of which memoization library to use but also optimizes the performance by ensuring that state selection is as efficient as possible. It can be particularly helpful in large-scale applications where selector reuse is critical and any performance improvement can make a noticeable difference to user experience.

For developers, the seamless experience is also propelled by advancements in error handling and development tooling. The use of <StrictMode> during development surfaces concurrency-related bugs by logging additional warnings and double-invoking functions that must be idempotent. While not a catch-all, this mode plays a crucial role in the early detection of potential issues, fostering robust practices during the development phase.

Error handling has also touched on the nuances of real-world usage. The Redux team's focus on optimizing performance and handling edge cases has culminated in an API that saves developers from writing their own subscription logic. This reflects an ecosystem-sensitive approach, where the middleware assumes responsibility for a variety of operational challenges, including those originating from third-party library interactions.

To provide a complete picture, it is necessary to assess these upgrades in practical terms. For example, when using RTK's configureStore method, the autoBatchEnhancer is now added to the store setup by default. This means developers gain performance improvements out-of-the-box without additional configurations. How can these enhancements impact your current workflows? Are there specific sectors in your application where the automatic batching and selector factories could be utilized for immediate gains? Such questions are pivotal when considering how to leverage these upgrades for tangible benefits in your development process.

Best Practices and Design Patterns

In the realm of large-scale application maintenance with React-Redux 9.0 and Redux v5.0.0, adopting best practices and design patterns is crucial for maximizing reusability and harnessing new feature sets. With modular codebases in view, using the Redux Toolkit's createSlice and createAsyncThunk functions supports logical encapsulation of related state and behaviors. By structuring state slices around features rather than data types, developers ensure more manageable and navigable code, leading to direct correspondence between state structure and UI architecture. Additionally, the Redux Toolkit's createEntityAdapter aids in standardizing CRUD operations, enhancing code reuse and reducing boilerplate.

The modernization of Redux requires a shift in mindset toward embracing encapsulated logic through the use of the Redux Toolkit. For example, employing the extraReducers builder callback within createSlice or the listener middleware allows for clean separation of cross-cutting concerns, aligning with robust design patterns like CQRS (Command Query Responsibility Segregation). Encapsulating side effects in such builder patterns ensures that they are co-located with relevant state slices, which improves readability and testability.

When considering performance and memory optimizations, mindful use of selector functions is paramount. With the advent of React Redux’s hooks API, useSelector permits fine-grained control over which state changes trigger component re-renders. Developers should strategize to write memoized selectors that compute derived data efficiently, which is pivotal for avoiding unnecessary renders in complex interfaces. This fine-tuning is fundamental in large applications where state changes frequently and views must reflect only pertinent updates.

To avoid common pitfalls, developers should be vigilant about over-fetching or duplicating data in state. While normalization is a suggested pattern to avoid data duplication, it requires strict discipline and understanding about data relationships and flow within the application. One must always weigh the complexity of maintaining a normalized state against the performance benefits it offers. The normalizr library, though not a Redux-specific tool, complements this practice by streamlining the normalization process.

Finally, with the enhanced support and stability provided by these synchronized major releases, it's beneficial to review the application's existing architecture against these recommendations. Are state slices organized optimally? Are side effects managed in a scalable way? Reflect on these thought-provoking questions while auditing your application in light of these Redux advancements to ensure alignment with the evolutions in the ecosystem. Making these strategic choices will pay dividends in application maintenance and development velocity.


In the article "React-Redux 9.0 and Redux v5.0.0: Synchronized Major Versions", the synchronized release of React-Redux 9.0 and Redux v5.0.0 is explored, highlighting the benefits and implications for developers. The article discusses the architectural and feature enhancements, breaking changes and migration path, performance and developer experience upgrades, as well as best practices and design patterns. The key takeaway is the importance of staying updated with the latest versions to take advantage of the streamlined development experience and improved state management. The challenging task for readers is to review their own Redux implementation and assess how to leverage the new features and enhancements in their own projects.

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