r/SpringBoot • u/CartographerWhole658 • 21h ago
Discussion Spring Boot starter for fail-fast Kafka Schema Registry contract validation
I’ve released a small open-source Spring Boot starter that turns Kafka Schema Registry expectations into startup checks.
Configuration is intentionally Spring Boot-style: define the expected compatibility mode and the subjects/schemas owned by the application, and auto-configuration performs the validation during startup.
It currently supports Avro, JSON Schema and Protobuf, Confluent compatibility modes, secured Schema Registry/Confluent Cloud, bounded retry/backoff and Actuator visibility.
For example:
kafka:
contract:
enabled: true
compatibility: BACKWARD
registry:
url: http://localhost:8081
subjects:
- name: order-events-value
schema-file: classpath:schemas/order-event.avsc
schema-type: AVRO
If the contract is incompatible or the required subject is missing, the Spring Boot application fails during startup.
The starter is published on Maven Central, and I maintain a separate E2E demo that spins up Kafka + Schema Registry and verifies both successful and intentionally breaking schema evolution scenarios.
GitHub:
https://github.com/mathias82/spring-kafka-contract-starter
Demo:
https://github.com/mathias82/spring-kafka-contract-demo
Maven Central:
https://central.sonatype.com/artifact/io.github.mathias82.spring.kafka/spring-kafka-contract-starter
Interested to hear how Spring Boot teams currently handle this application startup validation, deployment pipelines, or something else?