Apache Pulsar vs Buf 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.

Buf Schema Registry (BSR) is a Protobuf-aware registry for managing API schemas, dependencies, and client access as APIs change. Teams publish Protobuf files as versioned modules and resolve dependencies declared in buf.yaml. BSR generates hosted SDKs for supported languages and browsable documentation from schema versions and comments. Server-side lint and breaking-change policies can reject updates or hold them for review. The registry also shows which modules depend on another, helping teams identify affected consumers before deprecation. A GitHub Action handles build, lint, formatting, breaking-change checks, and publishing; the Buf CLI can connect to other CI/CD systems. RPC APIs are available through Connect, gRPC, and gRPC-Web. Community costs nothing and includes one private repository limited to 100 types plus unlimited public repositories. Teams costs $0.50 a month per type and includes a 30-day trial. Pro costs $5 a month per type with a $3000/month minimum spend. Enterprise pricing is custom.