A short debugging story about React.memo, prop drilling, and a missing useCallback.

The symptom

We had an editable table: one row per item, each row with a couple of text inputs. Every row component was wrapped in React.memo, specifically so that typing in one row wouldn’t force every other row to re-render. On a table with dozens of rows, that matters — otherwise every keystroke re-renders the whole table.

It didn’t work. Typing a single character in one row’s input made every row re-render, every time.