Solace vs HiveMQ: Plant MQTT Broker or Enterprise Event Mesh?

Solace vs HiveMQ is the comparison most manufacturers actually face when they plan a unified namespace across more than one plant. HiveMQ is an MQTT-first broker vendor whose products are built for devices, edge gateways and plant systems publishing by exception. Solace is a multi-protocol event broker that treats MQTT as one protocol among several and is designed to link many brokers into an enterprise event mesh. HiveMQ goes deeper on MQTT and Sparkplug; Solace goes wider across protocols, enterprise systems and sites. Which one fits depends on the layer of the architecture you are buying for.

This page sits under Solace alternatives in the Solace cluster. The vendor-neutral version of the question is choosing a UNS broker.

Solace vs HiveMQ: what each is built for

HiveMQ is built around MQTT. Its documentation states support for MQTT 3.1, 3.1.1 and 5.0, all three QoS levels, retained messages, persistent sessions and shared subscriptions. Around the broker sit HiveMQ Cloud (managed), HiveMQ Edge (a protocol gateway), a Kubernetes operator, the Swarm load-testing tool and an extension SDK, including enterprise extensions for data streaming integration. In February 2025 HiveMQ introduced HiveMQ Pulse, which it describes as a “distributed data intelligence platform” with data cataloguing, transformation and tools for a unified namespace.

Solace is built around routing many protocols across many sites. Its broker speaks SMF, MQTT 3.1.1 and 5, AMQP 1.0, JMS, REST and WebSocket, and translates between them. Brokers in plants, data centres and clouds link through Dynamic Message Routing. Solace positions itself in manufacturing as the enterprise backbone above plant brokers, not as a replacement for every plant broker.

Neither claim makes the other wrong. A plant’s SCADA, MES and dashboards all speak MQTT and want Sparkplug; an enterprise’s ERP, quality system and data platform often do not. The question is who your consumers are.

Solace vs HiveMQ compared on the same dimensions

Public facts as of October 2026, from each vendor’s documentation and the Eclipse Foundation.

Dimension	Solace Event Broker	HiveMQ
Primary design	Multi-protocol event broker and mesh	MQTT broker and platform
MQTT versions	3.1.1 and 5.0	3.1, 3.1.1 and 5.0
QoS 2	Converted to QoS 1	Supported
Shared subscriptions	QoS 0 only	Supported
Retained messages	Controlled Availability	Supported
Sparkplug listing (Eclipse)	Not listed; 2023 community test reported a pass	Community and Professional editions listed, plus Sparkplug Aware Extension
Sparkplug Working Group	Not a member	Steering Committee member
Other protocols	SMF, JMS, AMQP 1.0, REST, WebSocket, Kafka bridge	MQTT; other systems through extensions and HiveMQ Edge
Multi-site model	Dynamic Message Routing across brokers	Clustering, cloud service and edge bridging
Managed service	Solace Cloud	HiveMQ Cloud
Governance tooling	Event Portal, AsyncAPI	HiveMQ Pulse, data governance

Sources: Solace Using MQTT, HiveMQ introduction, the Eclipse Sparkplug compatible list and the Sparkplug Steering Committee minutes of June 2026.

The Sparkplug status of each

HiveMQ is on the list. The Eclipse Foundation’s compatible software list names HiveMQ MQTT Broker Community Edition and Professional Edition, and the HiveMQ Sparkplug Aware Extension, alongside Cirrus Link Chariot and NanoMQ. HiveMQ also sits on the Sparkplug Steering Committee.

Solace is not. On the Solace community forum in August 2023, a user reported running the Eclipse Sparkplug test kit against broker 10.5 and passing, after enabling retained message caching and adding memory. Solace has not appeared on the Eclipse list since, and its MQTT documentation does not mention Sparkplug. Our reading: Solace can carry Sparkplug traffic as an MQTT transport, self-tested, not Eclipse-listed. The detail is on Solace and Sparkplug B.

Why it matters in a plant. A Sparkplug host such as Ignition relies on the broker for retained STATE messages and correct Last Will handling to know whether edge nodes and the primary host are online. Retained messages being a Controlled Availability feature on Solace is the practical issue, more than the listing itself.

Where each sits in the ISA-95 stack

Placement is a pattern, not a rule. Both vendors sell products that can run at more than one layer. In the reference architectures both vendors and the wider UNS community publish, the MQTT-first broker serves the plant and the mesh links plants to the enterprise, joined by an MQTT bridge that forwards only the topics the enterprise needs.

Where each fits

HiveMQ fits a single-site or few-site unified namespace whose consumers are SCADA, MES, historians and dashboards that speak MQTT, where Sparkplug state handling matters, where a design needs QoS 2 or retained messages without caveats, and where the controls team will run the broker. HiveMQ also sells enterprise and cloud deployments, so “plant only” undersells it.

Solace fits when many plants must be linked to data centres and clouds, when ERP, quality or logistics systems need JMS, AMQP or REST, when guaranteed delivery and buffering across WAN links matter more than MQTT feature depth, and when an integration team will own the layer. An SAP-centric manufacturer may already have Solace through SAP advanced event mesh.

An illustrative case. A food manufacturer runs four plants, each with Ignition publishing Sparkplug data to a plant broker that dashboards, the historian and the MES consume. Corporate IT wants production counts, downtime events and quality holds in SAP, a cloud data platform and a supplier portal. Replacing four working plant brokers buys little. Bridging a curated set of topics from each plant into a mesh that buffers across the WAN, translates to the protocols each enterprise consumer speaks and filters by site is where an enterprise broker earns its cost. If the company had one plant and no enterprise consumers outside MQTT, the second layer would be overhead.

Both fit in the layered design above, which is the pattern Solace’s own UNS writing describes. The MQTT guide for manufacturing and the unified namespace guide cover the plant side.

Where it gets hard

• Sparkplug across a bridge. Birth, death and STATE messages must survive the boundary with their retained and Last Will semantics intact. Decide which side owns Sparkplug state, and test failover of the primary host.
• QoS mismatch. A flow published at QoS 2 in the plant arrives at QoS 1 on Solace. Consumers must tolerate duplicates.
• Topic mapping. MQTT + and # correspond to Solace * and >, but namespace conventions, case and reserved prefixes need a written mapping.
• Ownership. The plant broker usually belongs to OT and the mesh to IT. Without agreed ownership of the bridge, incidents bounce between teams.
• Two vendors, two licences, two upgrade cycles. Budget for both, and for the integration testing between them.
• Free editions are not equivalent. HiveMQ Community Edition is open source; Solace Standard Edition is free but its docs mark it not production deployable. Compare the editions you would actually run in production, with a written quote for each.
• Scale claims are the vendors’ own. Both publish connection and throughput figures from their own tests. Size with your plant’s real message rates and payloads in a pilot.

Designing that boundary is core IT/OT integration work. For the Kafka side of the same architecture, see Solace vs Kafka.