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#profiler

2 stories

Banner: React.memo list still re-rendered every row because inline objects and functions defeated memoization

Web Development Bug Report

React.memo list still re-rendered every row: inline objects and functions defeated memoization

Hannah Okafor · Feb 20, 2026 · 7 min read

We wrapped each row of a 1,500-item list in React.memo, yet typing in a filter box re-rendered every row. Each render passed a new style object and a new onSelect function, so the shallow prop comparison always failed. How we found it with the Profiler and fixed it with stable references.

Banner: a single React context provider triggering re-renders across a whole component tree

Web Development Bug Report

React context re-render storm: every keystroke re-rendered 600 components

John Nguyen · Nov 4, 2025 · 10 min read

Typing in our search box felt sticky, with INP above 400 ms on mid-range laptops. The React Profiler showed the entire product grid re-rendering on every keystroke because one app-wide context held both slow and fast-changing state. Splitting contexts and a selector store cut that to a handful of renders.