Chartboost does not pre-cache any creative content contained within an adm except for InLine VAST video files in iOS SDK v8.5.0+ and Android SDK v8.3.0+. The Webview begins downloading all other content (Javascript, images, etc.) once an ad begins rendering, after the SDK client calls for an ad to be shown. As such it is strongly recommended to make use of geo-optimized CDNs for hosting your ad markup assets.

Publishers are able to “cache” an ad placement prior to the time it will be shown. The ad markup will be cached and ready to be rendered, however assets (images, javascript, etc) in the payload are not prefetched or prerendered.