What is the difference between optimistic updates and pessimistic updates in a React data-mutation workflow?

Question

React Developer — Hard

What is the difference between optimistic updates and pessimistic updates in a React data-mutation workflow?

Accepted Answer

Optimistic updates in React immediately show the expected outcome in the UI before server confirmation, then adjust based on the actual server response. Pessimistic updates, on the other hand, wait for server confirmation before updating the UI.