Optimistic Updates with React Query: A Practical Guide

Ever found yourself wanting to make your React applications feel more responsive and snappy? That’s where optimistic updates come into play, and when combined with React Query, they become a powerful tool in your development arsenal.

What Are Optimistic Updates?

Optimistic updates are a UX pattern where we update the UI immediately after a user action, assuming the server request will succeed. Instead of waiting for the server’s response, we “optimistically” show the change to users right away. This creates a smooth, instant feel to your application.

Why Use Optimistic Updates with React Query?

React Query already makes data fetching and state management a breeze, but when you add optimistic updates to the mix, you get:

• Instant feedback for users
• Smoother user experience
• Better perceived performance
• Graceful error handling

Let’s dive into a practical example to see how this works.

Implementing Optimistic Updates

Here’s a real-world scenario: a todo list application where users can toggle task completion status.

const useTodoToggle = () => {
  const queryClient = useQueryClient();

  return useMutation(
    (todoId) => axios.patch(`/api/todos/${todoId}/toggle`),
    {
      onMutate: async (todoId) => {
        // Cancel outgoing refetches
        await queryClient.cancelQueries('todos');

        // Snapshot previous value
        const previousTodos = queryClient.getQueryData('todos');

        // Optimistically update todos
        queryClient.setQueryData('todos', (old) => {
          return old.map((todo) => {
            if (todo.id === todoId) {
              return { ...todo, completed: !todo.completed };
            }
            return todo;
          });
        });

        return { previousTodos };
      },

      onError: (err, todoId, context) => {
        // Rollback on error
        queryClient.setQueryData('todos', context.previousTodos);
      },

      onSettled: () => {
        // Refetch after error or success
        queryClient.invalidateQueries('todos');
      },
    }
  );
};

Best Practices for Optimistic Updates

1. Always Plan for Failures: Keep track of the previous state and implement proper rollback mechanisms.

2. Consider Network Conditions: Some users might have slow connections, making optimistic updates even more valuable.

3. Use Loading States Wisely: Even with optimistic updates, indicate background operations are happening.

4. Keep It Simple: Start with simple operations before implementing complex optimistic updates.

Conclusion

Optimistic updates are a game-changer for user experience, and React Query makes them surprisingly straightforward to implement. By following the patterns we’ve discussed, you can create interfaces that feel instantaneous while maintaining data integrity.

Remember, the goal is to balance user experience with data accuracy. When implemented correctly, optimistic updates can significantly enhance your application’s feel without compromising reliability.