Dispatcher

AEM’s caching and security layer — an Apache module in front of the Publish instances that caches rendered pages and assets on disk, filters which requests are allowed through at all, and balances the rest across the Publish farm; a page is rendered once and served from the dispatcher until an activation invalidates it

The reason a Publish page is fast and the reason a change sometimes does not show: the dispatcher serves the cached file until Author’s flush agent tells it not to. Its dispatcher.any configuration — the filter rules, the cache rules, the farm — is where a query string that busts the cache or a selector that must never reach Publish is decided. In AEM as a Cloud Service it is the same module, configured in the project repository and validated on deploy. A CDN usually sits in front of it, which makes three caches between a visitor and a component.