How do you profile and find performance problems in React?
Quick answer
Use the React DevTools Profiler to record renders, see which components rendered, how often, and why. Optimise the proven hotspot.
In detail
The Profiler shows a flamegraph of each commit, the render duration per component, and (with 'record why each component rendered') the trigger. Combine with the browser Performance tab for paint/layout costs. The discipline is to measure before changing anything, then verify the fix actually reduced renders/time.
Why interviewers ask this: Confirms you optimise with data, not guesswork.
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