Nice, have you come across NATS? https://nats.io. The server natively supports WebSockets. There are many clients including Deno, Node, WebSockets, Rust, Go, C, Python, etc.
In addition to stateless messaging, it supports durable streams, and optimized API layers on top like key-value, and object storage.
In addition to stateless messaging, it supports durable streams, and optimized API layers on top like key-value, and object storage.
The server also natively supports MQTT 3.1.1.