The Day I Learned What Actually Slows Down React Apps

Every React developer thinks performance issues come from the backend—until they learn the truth.

I learned mine in the middle of a sprint where the backend team kept saying, “API is fast… the UI isn’t.”

They were right.

The Moment of Realization

A junior dev pinged me:

“Why does our UI freeze if the API is super fast?”

I opened the Profiler.

One component—just one—was re-rendering 19 times for one change.

We didn’t have a slow API.
We had unnecessary work.

The Fix

We applied:

• React.memo for components with stable props
• Debounced handlers
• Avoided object spreading
• Lazy loading
• Bundle splitting

The fix wasn’t magic. It was discipline.

The Result

32% faster load.
Smoother UI.
A happier team.

Takeaway

React performance isn’t about doing “more”. It’s about avoiding the unnecessary.