## YYYY-MM-DD - [Memoize grid item re-rendering]

**Learning:** `useMemo` can significantly boost the performance of long list or grid components (like `PhotoGrid` component) that otherwise gets re-rendered on simple interactions like navigating the image lightbox. Running standard formatting `pnpm format` applies huge changes across entire directories, so it's generally best to format and clean up ONLY modified files to avoid huge diff pollution in code review.
**Action:** Be extremely cautious of running format/lint commands at the root codebase; specify only modified directories or files, or avoid formatting if it cascades globally. Focus on targeted memoization where state changes dictate expensive array mapping operations.