Retrieval module does permit indexed (i.e. immediate) retrievals of chunks you already have references to. However, this must be explicitly enabled with the EnableIndexedRetrievals parameter.
Retrievals can also be performed asynchronously if the declarative module is asynchronous.
Declarative FINSTs are controlled by two parameters: FINSTDurationTime (3 seconds) and NumberOfFINSTs (4 chunks). :recently-retrieved (null, false, true) can be used in retrieval requests.