Interview frequency: …
Short answer
It says productivity rises significantly when the computer responds within 400 milliseconds; beyond that, user attention begins to drift.
Explanation
When a network request takes longer than 400ms, provide immediate visual feedback to confirm that the request was received. Perceived-performance strategies include Skeleton Screens that suggest the page is taking shape, Optimistic UI that immediately shows a like or message before the server replies, and determinate progress indicators instead of slow spinners.
Common mistakes
- Leaving a button silent and without immediate animation for several seconds while waiting for the network, prompting repeated taps.
- Using spinners on every screen, making the system feel slow and heavy.