[splix]

I don't think that Java serialization is designed for such a small object with just two fields. It's designed for large and complex objects. Obviously it would be slower and much larger in size that a columnar implementation designed and heavily optimized for this scenarios. It's not a fair comparison and too far from a real use case.

Try with nested objects and at least a dozen of fields across this hierarchy. And different structure for each row. It's still not a use case for Java serialization, but at least closer to what a real code would do.

Same for Protobuf, I guess. Also the JSON serialization plays the same role more or less.

Maybe something like Avro Data Files is better for a comparison with columnar formats.