Latency numbers

• https://stackoverflow.com/questions/536300/what-is-the-shortest-perceivable-application-response-delay
• https://stackoverflow.com/questions/6880856/whats-the-minimum-lag-detectable-by-a-human
• https://ux.stackexchange.com/questions/42684/what-as-a-rule-of-thumb-is-the-maximum-tolerable-time-the-ui-thread-is-blocked
• https://stackoverflow.com/questions/164175/what-is-considered-a-good-response-time-for-a-dynamic-personalized-web-applicat
• These are the important latency numbers:

< 0.1 seconds = 100ms

• It is the limit for having the user feel that the system is reacting instantaneously
• No special feedback needed

< 1.0 seconds = 1000ms

• It is the limit for the user’s flow of thought to stay uninterrupted, even though the user will notice the delay.
• No special feedback needed but user lose the feeling of operating directly on the data.

< 10 seconds

• It is the limit for keeping the user’s attention focussed on the dialog
• Feedback to the user is needed indicating when the task is expected to be done
• Busy indicator can be useful in this scenario

> 10 seconds

• Feedback is especially important if the response time is likely to be highly variable
• Percent done indicator should be used to show feedback to the user.
• Percent done indicator benefits:
  • reassure that system has not crashed
  • indicate approximately how much long to wait
  • gives user something to look at and thus making wait less painful