Google Cloud Pub/Sub vs RabbitMQ

Google Cloud Pub/Sub is a cloud messaging service for asynchronous communication between services that produce messages and those that process them. It is intended for service-to-service use, including streaming analytics, data integration, middleware, and parallel task queues, rather than direct communication with end users or IoT clients. Communication typically has latency around 100 milliseconds. Synchronous cross-zone replication and per-message receipt tracking provide at-least-once delivery; Dataflow supports exactly-once processing of Pub/Sub streams. There are no shards or partitions, and provisioning scales automatically after quota is set. Message controls include seek and replay, dead letter topics, and attribute-based filtering. Pub/Sub offers fine-grained access controls, end-to-end encryption, and HIPAA compliance. It supports REST and gRPC APIs and client libraries for seven languages; API keys are not supported for authentication. The maximum message size is 10 MB. The free monthly tier is free for the first 10 GB of data per month. Pay-as-you-go is $40 a month beyond 10 GB, with throughput listed at $40 per TB and storage at $0.27 per GiB-month.

RabbitMQ is an open source messaging and streaming broker for application communication, including distributed microservices, real-time data, and IoT. Publishers can route messages to one or more consumers using routing, filtering, streaming, and federation. Message acknowledgements and replication across a cluster support delivery reliability, and delivery guarantees are configurable. Supported protocols include AMQP 0-9-1, AMQP 1.0, MQTT, STOMP, RabbitMQ Streams, HTTP, and WebSocket, including browser communication over WebSocket. Client libraries are available for Java, .NET/C#, Erlang, and other languages; the project also offers a community Docker image and Kubernetes operators. RabbitMQ can run in cloud or on-premises environments, on local machines and physical or virtual hardware, and in containers. Linux, Windows, and macOS are supported; z/OS, most mainframes, and systems with less than 100 MB of RAM are not. The free, self-managed Open Source RabbitMQ Server is offered under the Mozilla Public License 2.0 with best-effort community support. VMware Tanzu RabbitMQ is a commercial offering with 24/7 support and enterprise features; pricing is by contact.