@Override
  public Optional<NearestKeyValue> getNearestAfter(
      final SegmentIdentifier segmentIdentifier, final Bytes key) throws StorageException {
    try (final RocksIterator rocksIterator =
        db.newIterator(columnFamilyMapper.apply(segmentIdentifier), readOptions)) {
      rocksIterator.seek(key.toArrayUnsafe());
      return Optional.of(rocksIterator)
          .filter(AbstractRocksIterator::isValid)
          .map(it -> new NearestKeyValue(Bytes.of(it.key()), Optional.of(it.value())));
    }
  }
Instantiates a new RocksDb columnar key value snapshot.

@param db the db
@param metrics the metrics
plugins/rocksdb/src/main/java/org/hyperledger/besu/plugin/services/storage/rocksdb/segmented/RocksDBColumnarKeyValueSnapshot.java