Research papers in the design and analysis of the MQTT (Message Queuing Telemetry Transport) protocol focus on evaluating its architecture, performance, and suitability for resource-constrained IoT environments. MQTT is a lightweight, publish-subscribe messaging protocol designed for low-bandwidth, high-latency, and unreliable networks, making it widely used in IoT applications such as smart homes, industrial automation, and healthcare monitoring. Research in this area examines the protocol’s core components, including the broker, publishers, and subscribers, and analyzes its Quality of Service (QoS) levels, message delivery mechanisms, and topic-based filtering. Studies evaluate MQTT’s performance in terms of latency, throughput, packet loss, energy efficiency, and scalability under varying network conditions and device constraints. Several papers propose enhancements to the standard MQTT design, including optimized broker architectures, clustering, load balancing, and adaptive QoS management, to improve reliability and reduce network congestion. Security, though not originally a core focus of MQTT, is another critical area of analysis, with studies assessing authentication, authorization, and encryption mechanisms integrated with MQTT-S, TLS, and lightweight security extensions. Comparative analyses with other IoT protocols, such as CoAP and AMQP, provide insights into trade-offs in reliability, overhead, and energy consumption. Additionally, simulation and real-world testbed experiments are widely employed to study the protocol’s behavior under different traffic patterns, device densities, and mobility scenarios. Overall, the literature highlights that while MQTT’s lightweight and flexible design makes it suitable for a wide range of IoT applications, ongoing research continues to optimize its performance, enhance security, and ensure scalability in large, heterogeneous, and resource-constrained networks.