The majority of middleware and messaging systems in use were built in a time that did not have the concept of scale and real-time data that developers operate in today.
With the rise of Cloud Native and Microservices architectures as a design principle and the emphasis on simplicity, speed, and flexibility that come with it, developers need a messaging protocol to match.
Enter NATS. NATS is a remarkably lightweight messaging protocol, and extremely flexible and resilient. It is just a few MB in size, and can scale to publish tens of millions of message from a single server.