Loading Performance Design

Perceived vs Actual Performance

Users don't measure milliseconds. They measure whether the app feels fast.

Techniques

1. Optimistic updates: Show the result immediately, sync in background.

   • Like button: heart fills instantly, API call happens after.
   • Delete: item disappears instantly, undo available for 5s.

2. Progressive loading: Show content as it arrives.

   • Text before images.
   • Above-fold before below-fold.
   • Skeleton → content replacement.

3. Pre-loading: Anticipate next action.

   • Prefetch next page on link hover.
   • Preload resources for likely next steps.