We often see caching delays when trying to preview recently edited banners using the ?banner=... parameter. This is especially pronounced on mobile. It would be helpful and allow us to develop faster if there was some method to bypass or purge the caching when previewing, maybe another URL parameter.
(At the moment we can often bypass the cache by adding a random uselang=.. parameter to the url, but this is a bit hacky and produces noise in the logs. Plus it has to be changed every time the banner is edited.)