Apache Pulsar vs AxonOps Schema Registry

Apache Pulsar is a free, open-source distributed messaging and streaming platform built for cloud use. It supports message consumption with less than 10 ms latency and up to one million unique topics in a cluster. Configurable replication across geographic regions and automatic client failover to healthy clusters support multi-region deployments. Tenants and policies control access to data and actions, and can isolate brokers to limit noisy-neighbor effects. Maintained client libraries are available for Java, Go, Python, C++, Node.js, and C#. Built-in connectors move data to and from systems including Kafka, RabbitMQ, MySQL, PostgreSQL, MongoDB, Cassandra, and Elasticsearch. Pulsar Functions process messages with user-defined logic in Java, Python, or Go. Tiered storage can offload data from BookKeeper to blob storage such as S3 for unlimited retention. It can run in Docker or Kubernetes, with a Helm chart for Kubernetes. Encryption, authentication, and authorization are available but are not enabled by default. The 5.0.0-M2 milestone is for early testing and feedback, not production use.

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.