default void scheduleDeferred(String tag,
                                  Function<OptionalLong, OptionalLong> deadlineNsCalculator,
                                  Event event) {
        enqueue(EventInsertionType.DEFERRED, tag, deadlineNsCalculator, event);
    }
Schedule an event to be run at a specific time.

@param tag                   If this is non-null, the unique tag to use for this
                             event.  If an event with this tag already exists, it
                             will be cancelled.
@param deadlineNsCalculator  A function which takes as an argument the existing
                             deadline for the event with this tag (or empty if the
                             event has no tag, or if there is none such), and
                             produces the deadline to use for this event.
                             Once the deadline has arrived, the event will be
                             run.  Events whose deadlines are only a few nanoseconds
                             apart may be executed in any order.
@param event                 The event to schedule.
server-common/src/main/java/org/apache/kafka/queue/EventQueue.java