Serialization (Avro, Protobuf, JSON)

With Avro, is there a performance difference between the specific vs generic approach? What is preferred from the .NET client?

Working with the specific classes is much simpler and you should prefer this where possible. Use GenericRecord in scenarios where you need to dynamically work with data of any type.

I have not benchmarked this, but suspect the specific case to be a bit more efficient.