Consider a scenario, where a given Subject is consumed by multiple consumers. Now, one consumer needs an additional attribute to be processed. To support this change, a Producer has two options

Create a new topic with an additional attribute.

Update the existing topic with an additional attribute.  

Schema Registry is a distributed storage layer for schemas which uses Kafka as its underlying storage mechanism

https://docs.spring.io/spring-cloud-schema-registry/docs/current/reference/html/spring-cloud-schema-registry.html