Schema Registry and Subject

A schema registry stores schema definitions and supports controlled evolution. In Confluent Schema Registry, a subject groups versions to which a compatibility policy applies. A schema ID locates a schema within the registry scope, while a version locates an entry in one subject’s history. Version 2 need not have ID 2, and identical schemas can share an ID across subjects.

TopicNameStrategy commonly creates separate topic-key and topic-value subjects. RecordNameStrategy groups by the fully qualified record name across topics. TopicRecordNameStrategy combines the topic and record name. Choose the scope that matches the records intended to evolve together; unrelated event types are not automatically successive versions of one record.

A registered schema does not prove every emitted payload is valid, semantically correct, or authorized for a topic. Configure serializers, validation, producer permissions, and subject policy together. A consumer locating a valid schema ID still needs the appropriate reader and the expected contract.

Retain definitions and references for as long as retained records require them. Distinguish a temporary registry outage from a permanently unknown ID before deciding to retry or quarantine. The lab registry assigns a fresh ID to each registration and does not reproduce production schema reuse or access control.

Try the examples in Designing Topics and Event Contracts.

Reference: Confluent subjects and serialization.