Karapace vs Pact Broker

Karapace is a free, open-source implementation of the Kafka Schema Registry and Kafka REST Proxy. Its registry stores Avro, JSON Schema, and Protobuf schemas, keeps version histories, and checks compatibility between versions. The REST Proxy exposes HTTP APIs for producing and consuming Kafka events and handling administrative operations. Karapace implements the Confluent Schema Registry API and REST Proxy API versions 1 and 2, with version 2 as the default. A leader-and-replica design provides high availability and load balancing. Monitoring includes Prometheus-native metrics and OpenTelemetry traces and metrics, with optional Sentry reporting. Schema Registry authentication supports HTTP basic authentication and OAuth2/OIDC bearer-token validation; the REST Proxy forwards OAuth2 tokens instead of validating them. Karapace is self-hosted, requires Python 3.12 or newer, and installs from Docker images or source. Default Docker ports are 8081 for the Schema Registry and 8082 for the REST Proxy. It is offered at free.

Pact Broker shares consumer-driven contracts and verification results so teams can check compatibility between consumer and provider versions before deployment. It is designed for Pact contracts and also accepts contracts that can be represented as JSON. In a CI workflow, consumer builds publish contracts, provider builds retrieve and verify them, and consumers can use the can-i-deploy command to check whether deployment is safe. The broker includes a REST API, embedded API browser, generated documentation, service network diagrams, verification results and status badges. Webhooks can respond to contract changes by triggering actions such as a provider build or Slack notification. Deployment options documented include Docker and Terraform on AWS; PostgreSQL and SQLite are listed, though SQLite is not supported for long-term operation. Docker images support linux/amd64 and linux/arm64. The open-source self-hosted broker is free, with users responsible for hosting, operation, security, maintenance and upgrades. PactFlow plans are also listed: Starter is free, while Team costs $115.42 a month billed yearly or $127 a month billed monthly.