Discussion on: Redux is Dead: Long Live Redux Toolkit

Responding to each of those items:

createAsyncThunk

Yes, we do specifically recommend thunks as the default approach for side effects in Redux. That does not mean it's the only approach you can use. All the existing side effects libs (sagas, observables, 5 million others) still work fine. But the most common side-effect-y thing people need to do is basic AJAX fetching. Thunks are the simplest approach to doing that, and they have also always been the most commonly used approach.

FWIW, we're actually trying to nudge people away from using sagas as a default approach, especially for just data fetching. Don't get me wrong, sagas are a great power tool for complex async workflows that involve debouncing or "background thread"-type behavior. But they're overkill for basic data fetching, and one of the contributing reasons why people have long complained about the "boilerplate" associated with Redux. They shouldn't be the first tool people reach for when they want to fetch data, and they shouldn't be something that's "required to use with Redux".

So, since people were already doing this anyway, and the docs have always taught this "promise lifecycle actions" pattern from the beginning, it made sense to add createAsyncThunk to simplify the code that people were already writing.

References:

• Redux Style Guide: use thunks for async logic
• Why Redux Toolkit Uses Thunks for Async Logic
• Redux Fundamentals: Async logic
• Redux Essentials: Async Logic
• Redux Usage: Writing Logic with Thunks

createEntityAdapter

We have always recommend storing items in a normalized lookup table. In fact, I specifically wrote the Structuring Reducers: Normalizing State Shape docs page back in 2016 to officially start teaching that concept. But, we never had any built-in APIs that helped with any of that process. For any collection of items, you are very likely to do a number of CRUD-y type operations.

So, createEntityAdapter provides the reducers that implement those operations, and it's up to you to decide when and how it makes sense to run those reducers, and in response to what actions. They can be used as complete "case reducers", or as "mutating helper functions" inside of other Immer-powered reducers. Again, we just looked at "what are things people commonly have to write on their own?", and provided some generic implementations. You're free to use them, or not. All these APIs are pick-and-choose.

RTK Query

Aas mentioned with thunks, users have always used Redux stores as a server state cache. It's just that Redux never included anything built in to help with that process. So, you inevitably ended up having to write all your own logic to manage loading state, make the requests, define the actions, dispatch the actions, save the data, handle errors, etc. The growth of React Query and Apollo have shown that the community has become much more interested in "server state caching" than "state management" in many cases. Redux makes a perfectly fine place to cache data, but writing the code to do that yourself is a pain.

So, once again, we built a set of APIs that just simplifies what everyone else has been doing by hand already, and provides a best-in-class API for dealing with server state caching.

RTK Query is built on top of createAsyncThunk and the other APIs in Redux Toolkit. As the RTK tagline says, it's "The official, opinionated, batteries-included toolset for efficient Redux development". Yes, RTK Query is effectively a second library, but it it's also very reasonable to include it in the actual RTK package. For one thing, some enterprises have difficult approval processes to go through to add additional libraries. By including the RTK Query APIs directly in the RTK package, you get them "for free" just by bumping to RTK 1.6+.

And yes, not only do the RTK APIs all tree-shake so you only pay for what you use, RTK Query itself is an entirely separate entry point, so none of it gets included in the app unless you specifically import it.

As you can see, all of these APIs have a common theme:

• These are things people were always doing with Redux, and have been taught in our docs
• Because Redux didn't include anything built-in for this purpose, people were having to write this code by hand, or create their own abstractions
• So we created standardized implementations of all these concepts that people could choose to use if they want to, so that people don't have to write any of this code by hand in the future.

Hopefully that helps clarify why these APIs exist :)