Outbound answers the host warms before Drupal asks for them.
A Worker cannot fetch synchronously, so the deferred tier refuses the first request for a URL.
A URL the host can name from the schedule, without running Drupal and with no side effect at
the far end (a GET against a published endpoint), is fetched ahead so the render hits the cache.
Not eligible: a login callback (the host owns that route), a search query inside a render, and
a cache backend (the object's SQLite replaces it).
Outbound answers the host warms before Drupal asks for them.
A Worker cannot fetch synchronously, so the deferred tier refuses the first request for a URL. A URL the host can name from the schedule, without running Drupal and with no side effect at the far end (a GET against a published endpoint), is fetched ahead so the render hits the cache. Not eligible: a login callback (the host owns that route), a search query inside a render, and a cache backend (the object's SQLite replaces it).