The React Performance Rabbit Hole I Fell Into (And How I Climbed Out)

Recently, while working on a project with React and Next.js, I encountered several performance challenges that taught me valuable lessons I'm excited to share with you. This post details my experiences and the solutions I discovered, hoping it will serve as both inspiration and practical guidance for your own React development journey. 🚀

Better Performance = Better User Experience

Let's be real - nobody has time for slow apps. Not me, not you, and definitely not our users. People want to get things done fast.

Strong performance builds trust in your app and brand. It shows you respect your users' time. And in 2025, with attention spans shorter than ever, performance isn't just nice to have.

The Silent Killer: Unnecessary Re-renders

In my project, I discovered React components were re-rendering 3-4x more often than needed. These silent re-render cycles are particularly insidious because:

• They don't crash your app, making them easy to overlook
• Performance degradation compounds gradually as features get added
• Mobile users pay double with slower processors + re-render penalties

What makes this especially tricky is React's "render everywhere just in case" philosophy. While great for correctness, it means components often update when nothing visually changes.

Here's how I fought back

1. Identifying Performance Bottlenecks

I started by analyzing runtime performance with Chrome DevTools. The Performance panel became my best friend during optimization:

• Look for components that render frequently
• Identify render cascades (when one component update triggers a waterfall of child updates)
• Spot components with abnormally long render times

2. Embracing Memoization Strategically

React gives us powerful tools to avoid unnecessary work:

• memo prevented my complex UI components from re-rendering when their props hadn't changed
• useMemo helped me cache expensive calculations
• useCallback kept function references on every render, particularly important for optimising callbacks passed to child components

Memoization isn't free - I found that applying these tools thoughtfully (rather than everywhere) gave me the best results. The upcoming React Compiler is getting better at handling simple optimizations automatically, complex components still benefit from manual memoization.

3. Function Definitions Matter More Than You Think

Something I didn't realize at first: defining functions inside your render scope creates new functions on every render, triggering re-renders in child components even with memo.
Moving these definitions outside the component or wrapping them with useCallback made a noticeable difference.

4. Leveraging DevTools

Rather than guessing where performance issues might be, I learned to rely on Chrome DevTools' Performance panel to identify actual bottlenecks. Here are some other tools:

• Use the Profiler tab in React DevTools
• Start a Lighthouse audit in the Chrome DevTools
• Track rerenders of specific components with Why did you render?

What's Working For You?

I'm curious - have you hit similar walls with React performance? Have you tried any of these techniques? Let me know in the comments ✨