Kafka applications are event based, and leverage stream processing to continuously process input data. If you’re using Kafka, then you can embed an analytic model natively in a Kafka Streams or KSQLapplication. There are various examples of Kafka Streams microservices embedding models built with TensorFlow, H2O or Deeplearning4j natively.
It is not always possible or feasible to embed analytic models directly due to architectural, security or organizational reasons. You can also choose to use RPC to perform model inference from your Kafka application (bearing in mind the the pros and cons discussed above). You can visit my project for an example of gRPC integration between a Kafka Streams microservice and locally hosted TensorFlow Serving container for making predictions with a hosted TensorFlow model.
There are a couple separate and interesting patterns here.