Real-Time Messaging Protocols: WebSockets, SSE, gRPC, Long Polling, and MQTT Compared
I have built real-time features into more systems than I can count: chat, live dashboards, IoT telemetry pipelines, collaborative editors, trading feeds, notification systems. Every one of them started with the same question: which protocol? The answer has never been the same twice, and the wrong choice has cost me weeks of rework more than once. WebSockets get all the attention. SSE gets overlooked. gRPC streaming gets misunderstood. Long polling gets dismissed too quickly. MQTT gets ignored entirely outside IoT circles. Each of these protocols solves a different problem, and the differences become painfully obvious only after you have built, deployed, and tried to scale the wrong one.