Persistence and Rehydration

RTK Query supports rehydration via the extractRehydrationInfo option on createApi. This function is passed every dispatched action, and where it returns a value other than undefined, that value is used to rehydrate the API state for fulfilled & errored queries.

See also Server Side Rendering.

info

Generally, persisting API slices is not recommended and instead, mechanisms like Cache-Control Headers should be used in browsers to define cache behaviour. Persisting and rehydrating an api slice might always leave the user with very stale data if the user has not visited the page for some time. Nonetheless, in environments like Native Apps, where there is no browser cache to take care of this, persistance might still be a viable option.

Redux Persist

API state rehydration can be used in conjunction with Redux Persist by leveraging the REHYDRATE action type imported from redux-persist. This can be used out of the box with the autoMergeLevel1 or autoMergeLevel2 state reconcilers when persisting the root reducer, or with the autoMergeLevel1 reconciler when persisting just the api reducer.

TypeScript

redux-persist rehydration example

import type { Action, PayloadAction } from '@reduxjs/toolkit'
import { createApi, fetchBaseQuery } from '@reduxjs/toolkit/query/react'
import { REHYDRATE } from 'redux-persist'

type RootState = any // normally inferred from state

function isHydrateAction(action: Action): action is PayloadAction<RootState> {
  return action.type === REHYDRATE
}

export const api = createApi({
  baseQuery: fetchBaseQuery({ baseUrl: '/' }),
  extractRehydrationInfo(action, { reducerPath }) {
    if (isHydrateAction(action)) {
      if ((action as any).key === 'key used with redux-persist') {
        // when persisting the api reducer
        return action.payload
      }

      // When persisting the root reducer
      return action.payload[reducerPath]
    }
  },
  endpoints: (build) => ({
    // omitted
  }),
})

JavaScript

redux-persist rehydration example

import { createApi, fetchBaseQuery } from '@reduxjs/toolkit/query/react'
import { REHYDRATE } from 'redux-persist'

function isHydrateAction(action) {
  return action.type === REHYDRATE
}

export const api = createApi({
  baseQuery: fetchBaseQuery({ baseUrl: '/' }),
  extractRehydrationInfo(action, { reducerPath }) {
    if (isHydrateAction(action)) {
      if (action.key === 'key used with redux-persist') {
        // when persisting the api reducer
        return action.payload
      }

      // When persisting the root reducer
      return action.payload[reducerPath]
    }
  },
  endpoints: (build) => ({
    // omitted
  }),
})