A Stream Processor is responsible for consuming data from stream sources (such as Kafka, Kinesis, etc.) and loading it directly into the online (and optionally the offline store).

A Stream Processor abstracts over specific technologies or frameworks that are used to materialize data. An experimental Spark Processor for Kafka is available in Feast.

If the built-in processor is not sufficient, you can create your own custom processor. Please see this tutorial for more details.