At which point is an IndexedDB request or transaction sent

Question

from the examples provided here and here

They show creating a request and then attaching the onerror and onsuccess handlers after the request

Answer 1

Could it be that if the request is quick enough would the handlers not be attached and therefore not trigger

Nope, you don't have to worry about that. The event is queued up and only fired when control returns to script next time, at which point your handlers will have been assigned.