private boolean isDeletedCacheEntry(final KeyValue<Bytes, LRUCacheEntry> nextFromCache) {
        return nextFromCache.value.value() == null;
    }
Merges two iterators. Assumes each of them is sorted by key

@param <K>
@param <V>
streams/src/main/java/org/apache/kafka/streams/state/internals/AbstractMergedSortedCacheStoreIterator.java