Why are some actions, such as running a report or opening an incident, slow the first time they are executed in BUI?
Browser User Interface (BUI)
The Agent Browser UI (BUI) has an additional caching layer to increase locality which in turn provides faster performance in the BUI than would otherwise be achievable. In order to see the performance improvement when operating in the BUI, this additional mid-tier cache needs to be initially populated with data.
Once you have opened or created 1 record (of a type), then the cache is primed for that record type. This type of slowness will occur only the first time and effects certain actions such as running a report, opening an incident, creating a contact etc. Once the initial action has been executed, that record type becomes cached at the mid-tier caching level, which in turn makes subsequent actions of the same type faster. This is expected behavior and is intended to help increase overall performance of the Agent Browser UI.