What is MQTT?

MQTT (Message Queuing Telemetry Transport) is a lightweight, publish/subscribe messaging protocol designed for low-power, low-bandwidth, or unreliable networks. From the early days of monitoring oil pipelines over satellite links to today’s massive IoT deployments, MQTT has evolved into a flexible and powerful messaging system used around the world. We’ll walk through the publish/subscribe model, how brokers and clients communicate, and how topics and wildcards let you organize data in a clean, hierarchical way. You’ll also learn about MQTT features like Quality of Service levels, retained messages, and Last Will and Testament. These are tools that give you control over reliability, delivery guarantees, and device health monitoring even in unreliable networks. We also cover the key upgrades introduced in MQTT version 5, including message expiry, user properties, shared subscriptions, and improved request/response handling. Whether you're building home automation projects, industrial control systems, or large-scale sensor networks, these features help you design systems that are scalable, efficient, and easier to reason about. We’ll finish with essential security considerations to help you protect your MQTT setup, including TLS, authentication, access control lists, and basic hardening practices. If you're new to MQTT or want a stronger conceptual foundation, this video gives you a solid conceptual understanding of how MQTT works and important terminology you’ll need to implement IoT device networks using the protocol.