The REAL reason React apps slow down — and the 3 tools to fight it

React felt fast… until it didn’t.

Ever built a React app that was buttery smooth at first, but once your app grew, your UI suddenly lagged like an old laptop running 50 Chrome tabs?

That’s usually when people discover the "holy trinity" of React performance optimization:

React.memo

useCallback

useMemo

But here’s the truth:
👉 Most devs either overuse them or don’t actually know what’s happening under the hood.

I just finished writing an in-depth breakdown that goes beyond the usual surface-level definitions.
Instead of just “React.memo prevents unnecessary re-renders” 🙄, I dug into how React reconciles components, why references break equality checks, and when memoization actually helps vs hurts.

🔍 Covered in the guide:

What really happens during React’s reconciliation cycle.

Why useCallback/useMemo aren’t “free” optimizations.

Common pitfalls (like wrapping everything in memoization).

A mental model to know exactly when to use them — and when not to.

If you’ve ever wondered why your memoized code still re-renders or felt guilty sprinkling useMemo everywhere withoutunderstanding… this might help.

Would love feedback from the community:
👉 Do you consciously think about reconciliation & referential equality when optimizing?
👉 Or do you mostly rely on profiling after things feel slow?

Link to full write-up (if you want): Click Here