HTTP Caching stores recently retrieved data in a local storage location, so that it can be served up for subsequent requests quickly, without having to go to the original source. The original source is often over a network connection, so caching locally saves time, and makes the network capacity available for other uses. Most caches have a time to live value associated with them. This ensures that after a preset period of time the local copy is removed, and the original source is queried to get a current copy of the data. This timeout preset can be set as required dependent on how dynamic the data in question is. If it’s fairly static in nature then the timeout person can be set to a few hours, or event days. If the data is dynamic then the caching for it can be a few seconds, or even disabled completely so that the current version is always requested when needed.