Thanks for the reply, but I am not using it for managed state, but rather for the raw state
In my implementation I have the following

class DataProcessorKeyed extends CoProcessFunction[WineRecord, ModelToServe, Double]{

  // The managed keyed state see
  var modelState: ValueState[ModelToServeStats] = _
  var newModelState: ValueState[ModelToServeStats] = _
  // The raw state -
  var currentModel : Option[Model] = None
  var newModel : Option[Model] = None

Where current and new model are instances of the trait for which I implement serializer
According to documentation <>

“Raw State is state that operators keep in their own data structures. When checkpointed, they only write a sequence of bytes into the checkpoint. Flink knows nothing about the state’s data structures and sees only the raw bytes.”

So I was assuming that I need to provide serializer for this.
Am I missing something?

Boris Lublinsky
FDP Architect