Karapace

What Karapace is

Karapace is a free, open-source implementation of the Kafka Schema Registry and Kafka REST Proxy. Its registry keeps schemas in one place, tracks their versions, and checks compatibility between versions. It supports Avro, JSON Schema, and Protobuf. The REST Proxy provides HTTP APIs for producing and consuming Kafka events and carrying out administrative operations. Karapace implements the Confluent Schema Registry API and Confluent REST Proxy APIs v1 and v2, with v2 as the default. A leader-and-replica design provides high availability and load balancing across instances. For observability, Karapace exposes Prometheus-native metrics and integrates with OpenTelemetry for traces and metrics; Sentry error reporting can also be enabled. Registry authentication supports HTTP basic authentication and OAuth2/OIDC bearer-token validation. The REST Proxy forwards OAuth2 tokens to Kafka and the Schema Registry rather than validating them itself. Karapace is self-hosted and requires Python 3.12 or newer; it can be installed from Docker images or source. The default Docker setup exposes the Schema Registry on port 8081 and the REST Proxy on port 8082. Aiven describes Karapace as an Aiven-built open-source registry and proxy for Aiven for Apache Kafka.

Who it suits

Karapace suits teams that need a self-hosted registry for Kafka schemas and HTTP access to produce or consume Kafka events. It is relevant to teams using Avro, JSON Schema, or Protobuf that want version tracking, compatibility checks, and monitoring integrations.

Limits

Schema normalization is currently supported only for Protobuf, and Karapace does not implement every Confluent Schema Registry normalization feature. JSON Schema references are unsupported; Avro references require Karapace version 6.1.0 or newer.

Getting started

1. Open the Karapace website.
2. Choose Docker images or source as the installation route.
3. Provide Python 3.12 or newer for installation.
4. Configure the Docker setup to expose the Schema Registry on port 8081 and REST Proxy on port 8082 by default.
5. Select the schema format and configure registry authentication if needed.

Verdict

Choose Karapace if you need a free, self-hosted Kafka schema registry and REST Proxy with Confluent API compatibility. Its schema formats, version checks, and monitoring integrations cover several common registry needs. Review its normalization and schema-reference limits against your requirements before adopting it.