AxonOps Schema Registry vs Karapace
AxonOps Schema Registry
github.comKarapace
aiven.ioSide by side
| Figure | AxonOps Schema Registry | Karapace |
|---|---|---|
| Price from | Free | $35/mo |
| Free plan | Yes | Yes |
| Free trial | — | — |
| Open source | Yes | — |
| Linux | Yes | Yes |
| API | Yes | Yes |
| Self-hosted | Yes | Yes |
| Plans published | 2 | 2 |
| Spec score · Schema Registry Software | 8.6 (#2) | 8.1 (#8) |
| Authentication | Built-in authentication methods include Basic, API keys, JWT, LDAP/Active Directory, OIDC, and mutual TLS. | Karapace supports OAuth 2.0/OIDC authentication for Schema Registry and the REST Proxy. |
| Company headquarters | LinkedIn identifies AxonOps headquarters as London, United Kingdom. | Aiven says it is headquartered in Helsinki, Finland. |
| Deployment | The registry is a single statically linked binary of about 50 MB and can run as a Docker container or be built from source. | The project documents Docker-based setup and installation from source with pip. |
| Headquarters | London, United Kingdom | Helsinki, Finland |
| Notable limit | The Cassandra storage backend requires Cassandra 5.0 or later; earlier versions are unsupported. | Karapace’s built-in schema backup functionality was removed in version 6.0.0 and is no longer maintained in the project. |
| What it does | AxonOps Schema Registry is a Kafka schema registry designed as a drop-in replacement for Confluent Schema Registry. | Karapace is an Aiven-built open-source Schema Registry and REST Proxy for Aiven for Apache Kafka. |
Plans
In their own words
AxonOps Schema Registry
AxonOps Schema Registry is a free, Apache 2.0-licensed service for managing Apache Kafka schemas as an API-compatible replacement for Confluent Schema Registry. It handles Avro, Protobuf, and JSON Schema, including references and seven compatibility modes. Schemas can be stored in PostgreSQL, MySQL, or Cassandra, without requiring Kafka as the storage backend. The project says existing Confluent serializers and Java, Go, and Python Kafka clients can connect by changing the registry URL. Security options include Basic Auth, API keys, JWT, LDAP/AD, OIDC, mTLS, four RBAC roles, rate limiting, and TLS certificate auto-reload. Audit events can go to stdout, files, syslog, or webhooks. Client-side field encryption supports DEK/KEK registries and HashiCorp Vault or OpenBao Transit. Data contracts add metadata and rules. A beta MCP server supports several AI clients. It runs self-hosted on Linux, as a Docker container, or from source.
Karapace
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.