CDN will help the fastest loading of all reasources.
CDN Invalidation is some kind of cache refresh of the CDN. Once an object is cached, it usually remains in the cache until it expires or is evicted to make room for new content. Our configuration files are usually cached for the fastest performance, but sometimes we would need to refresh the cache. That is most of the time when the tracker settings have changed and the settings must apply. For the free trackers, usually, CDN Validation is taking time in 12 or 24 hours. For PRO trackers - settings are refreshed immediately.