// the find
zentures/surgemq
(Unmaintained) High-Performance MQTT Server and Client Libraries
SurgeMQ is an in-memory MQTT 3.1.1 broker and client library written in Go, once positioned as a high-throughput alternative to Mosquitto/Paho. It's for nobody building anything new today — the README itself says it's unmaintained and points you to VolantMQ instead.
Sessions, topics, and auth are behind Go interfaces (SessionsProvider, TopicsProvider, Authenticator) so the in-memory defaults are swappable in theory, even though only the mem implementations actually shipped. It supports the full QoS 0/1/2 range plus will and retained messages, and was validated against real client stacks (libmosquitto, Paho C/Go/Python conformance suite) rather than just its own test suite. The publish/subscribe fan-in/fan-out benchmarks (400k-750k msgs/sec on a single machine) show the core message-passing path was genuinely fast for its era.
Last commit was 2020, the author explicitly abandoned it and recommends VolantMQ — this is a dead project, not a slow-moving one. Everything is in-memory only: a server restart wipes all sessions, subscriptions, and retained messages, and the roadmapped session persistence never landed. It fails two of the ten Paho conformance tests because message redelivery on reconnect and offline message queueing were never implemented, which matters if you actually need QoS1/2 reliability guarantees. The throughput numbers are a single 2014 MacBook Pro microbenchmark with no production deployment evidence behind them.