useReducer, useMemo & useCallback Explained Like You Actually Use React

Most React developers know useReducer, useMemo, and useCallback.

Very few developers use them correctly.

Some overuse them.
Some avoid them.
Some copy-paste them just to silence re-renders without understanding why.

This article is about when, why, and how these hooks actually matter in real React apps — especially large, production-scale UIs.

Let’s break them down properly.

optimization hooks

Part 1: useReducer — When useState Starts Breaking Down

The Real Problem with useState

useState is perfect… until it isn’t.

If your component has:

• Multiple related state values
• Complex update logic
• State transitions that depend on previous state
• Business rules (not just UI toggles)

Your component slowly turns into this:

setIsLoading(true);
setError(null);
setData(null);
// later
setData(response);
setIsLoading(false);

Now imagine:

• Errors