Some of our content sources make backend calls to private APIs. These APIs are hosted externally to ARC and are available only via HTTPS. The initial TLS connection requires at least 3 round trips of packets to be exchanged before an HTTP request can be made. This can easily add 100ms or more latency to any external HTTPS request from PageBuilder.
It's best practice to use a connection pooling mechanism with keep-alive, allowing the user to keep those TLS channels open for further requests. Even though this feature is supported by NodeJS, PageBuilder does not support it.
Built in caching does little for services such as search and personalization.