Pessimistic Updates

Pessimistic Updates Overview

At its core, pessimistic updates is about doing one thing well in Redux. Once you understand the pattern, you can apply it consistently across projects and teams.

Good pessimistic updates pays off across the whole project: fewer surprises, easier collaboration, and smoother onboarding. The snippet below is a solid starting point.

import { createApi, fetchBaseQuery } from '@reduxjs/toolkit/query/react';

export const api = createApi({
  reducerPath: 'api',
  baseQuery: fetchBaseQuery({ baseUrl: '/api' }),
  endpoints: (builder) => ({
    getUsers: builder.query({ query: () => 'users' }),
    addUser: builder.mutation({
      query: (body) => ({ url: 'users', method: 'POST', body }),
    }),
  }),
});

export const { useGetUsersQuery, useAddUserMutation } = api;

RTK Query handles data fetching, caching, and auto-generated React hooks for you.

Pessimistic Updates Example

const slice = createSlice({ name, initialState, reducers });
const store = configureStore({ reducer: { key: slice.reducer } });
// dispatch(slice.actions.something())

• Start from a minimal Pessimistic Updates example and grow it only as needed.
• Keep things explicit so Pessimistic Updates behaves the same for everyone on the team.
• Name things clearly so teammates understand your Pessimistic Updates at a glance.
• Verify Pessimistic Updates works as expected before relying on it in important work.

Redux Cheatsheet

Quick Redux Toolkit reference related to pessimistic updates.

How Pessimistic Updates Works in Redux

Pessimistic Updates follows Redux's predictable data flow: components dispatch actions, reducers compute the next state from the previous state and the action, and subscribed components re-render.

RTK Query handles data fetching, caching, and auto-generated React hooks for you.

• State lives in a single, read-only store.
• Actions are the only way to describe a change.
• Reducers are pure functions that return the next state.
• Redux Toolkit removes most boilerplate with slices and thunks.

Practical Guidance for Pessimistic Updates

In modern apps, pessimistic updates should use Redux Toolkit rather than hand-written Redux. Keep state minimal, colocate logic in slices, and use RTK Query for server data.

Common Mistakes

• Skipping edge cases and error handling when using pessimistic updates.
• Not verifying the result of pessimistic updates before moving on.
• Over-complicating pessimistic updates before you actually need the extra flexibility.
• Ignoring documentation, which makes pessimistic updates hard for the next person to follow.

Key Takeaways

• Pessimistic Updates is a core part of working effectively with Redux.
• Start small and keep pessimistic updates focused on a single goal.
• Apply consistent patterns so pessimistic updates scales across your project.
• Practise and document pessimistic updates to keep your workflow maintainable.