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by the way in 2005 I programmed using very funny PHP framework PRADO that was sending every change in the UI to the server. Boy it was slow and server heavy. This was the direction we should have never gone...
not a good example. i can't find it now, but there was a story/comment about a realtor app that people used to sell houses. often when they were out with a potential buyer they had bad internet access and loading new data and pictures for houses was a pain. it wasn't until they switched to using a frontend framework to preload everything with the occasional updates that the app became usable.
low latency affects any interaction with a site. even hackernews is a pain to read over low latency and would improve if new comments where loaded in the background. the problem creeps up on you faster than you think.
It can also be imposed by the client, e.g. via a https://en.wikipedia.org/wiki/Web_accelerator