Karapace vs WarpStream BYOC Schema Registry

Karapace is Aiven’s open-source Schema Registry and REST Proxy for Aiven for Apache Kafka. The registry stores and versions schemas, then checks compatibility before a changed schema is published. It accepts Avro, Protobuf, and JSON Schema, with references supported for Avro and Protobuf. Compatibility modes include NONE, BACKWARD, BACKWARD_TRANSITIVE, FORWARD, FORWARD_TRANSITIVE, FULL, and FULL_TRANSITIVE. The REST Proxy exposes HTTP endpoints for producing and consuming Kafka events, so scripts, curl, and HTTP services can work with events. OAuth 2.0/OIDC authentication is available for both components. Registry ACLs and OIDC role-based rules can limit operations, including by HTTP method. Example identity providers include Auth0, Okta, Google Identity Platform, and Azure. Deployment documentation covers Docker and installation from source with pip; the API is stated to support Schema Registry 6.1.1 operations. Karapace is available in Aiven’s Kafka free tier for learning, prototyping, and evaluation. The Free plan costs nothing, while Developer costs $35 a month.

WarpStream BYOC Schema Registry stores and serves schemas for Kafka records through a REST server compatible with Confluent’s Schema Registry API. It supports Avro and protobuf, while WarpStream Agents validate records and can reject invalid data or emit metrics. The stateless, zero-disk registry stores schemas in the customer’s object storage, and WarpStream says they remain in that cloud account. Schema Linking migrates schemas from a Confluent-compatible registry while preserving IDs and compatibility rules. Authentication options include Basic Authentication, TLS and mutual TLS. Customers create a Schema Registry Virtual Cluster in the console or API, then deploy an agent using the Kafka Agents binary; agents emit logs and metrics. Each registry allows 100,000 schema versions and each schema 1 MB, with support-requested increases. Plans are Dev at $0.03 a month, Fundamentals at 0.17 USD, Pro at 0.52 USD, and Enterprise with no listed price. Cluster minutes use 15-minute billing intervals.