OptionalInt keyToBrokerId(K key) {
        Optional<FulfillmentScope> scope = fulfillmentMap.getKey(key);
        return scope
            .map(fulfillmentScope -> OptionalInt.of(fulfillmentScope.destinationBrokerId))
            .orElseGet(OptionalInt::empty);
    }
Disassociate a key from the currently mapped brokerId. This will send the key
back to the Lookup stage, which will allow us to attempt lookup again.
clients/src/main/java/org/apache/kafka/clients/admin/internals/AdminApiDriver.java