Google Cloud Pub/Sub vs HiveMQ MQTT Broker

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.

HiveMQ MQTT Broker provides event-driven messaging between connected devices and enterprise systems. It supports MQTT 3.1.1 and MQTT 5.0, with persistent messages stored to disk, offline queuing, and quality-of-service support. Dynamic clustering lets operators add or remove broker nodes while the cluster runs. Extensions connect to streaming services, databases, data warehouses, and security services, with Kafka, Amazon Kinesis, and Google Pub/Sub listed as examples. Security options include TLS 1.2/1.3, mutual TLS, fine-grained access controls, pluggable authentication such as OAuth 2.0 and LDAP, and audit logging. The self-managed broker can run on private, hybrid, and public clouds, with images for Kubernetes, OpenShift, and DC/OS. In evaluation mode without a valid license, it supports up to 25 client connections. HiveMQ describes the broker as intended for large-scale IoT deployments and mission-critical enterprise operations. Plans include a free option; Launch is $299 a month and Run is $499 a month. Other listed plans have no price listed.