spring-cloud-dataflow-samples/function-samples/kstreams-word-count/src/main/resources/application.yml

spring.cloud.stream.kafka.streams:
  binder.configuration:
    commit.interval.ms: 1000
    default.key.serde: org.apache.kafka.common.serialization.Serdes$StringSerde
    default.value.serde: org.apache.kafka.common.serialization.Serdes$StringSerde
  bindings.input.consumer.application-id: kstream-word-count-sample