MQTT vs REST: What are the differences?

Introduction

In this article, we will discuss the key differences between MQTT and REST protocols. MQTT (Message Queuing Telemetry Transport) and REST (Representational State Transfer) are both widely used in the field of Internet of Things (IoT) and play different roles in enabling communication between devices and systems.

1. Protocol design: MQTT is a publish-subscribe messaging protocol, while REST is an architectural style. MQTT follows a lightweight design and is optimized for constrained devices and high-latency networks. On the other hand, REST uses standard HTTP methods (GET, POST, PUT, DELETE) for communication and can be implemented over any network protocol.

2. Communication pattern: MQTT uses a publish-subscribe communication pattern, where clients (publishers) send messages to topics and other clients (subscribers) receive those messages by subscribing to those topics. In contrast, REST follows a client-server communication pattern, where clients send requests to servers and get responses back.

3. Statelessness: REST is stateless, meaning that each request from the client to the server should contain all the necessary information for the server to understand and process the request. On the other hand, MQTT supports session management and can maintain stateful connections between clients and brokers.

4. Message size and overhead: MQTT is designed to be lightweight and efficient, making it ideal for low-bandwidth or unreliable networks. It has a small message overhead and allows for smaller payload sizes. In contrast, REST messages typically have more overhead due to the use of HTTP headers and require larger message sizes.

5. Quality of Service (QoS) levels: MQTT provides different levels of Quality of Service to ensure message delivery reliability, including QoS 0 (at most once), QoS 1 (at least once), and QoS 2 (exactly once). REST does not provide built-in QoS mechanisms and relies on the underlying HTTP protocol for reliability.

6. Scalability and resource usage: MQTT is designed to handle a large number of connected clients efficiently, making it a good choice for scalable IoT deployments. REST may require more server resources to handle a high number of concurrent connections and requests.

In summary, MQTT is a lightweight publish-subscribe messaging protocol optimized for constrained devices and networks, while REST is an architectural style based on client-server communication over standard HTTP methods. MQTT supports stateful connections, has lower message overhead, provides QoS levels, and is more scalable, while REST is stateless, has higher message overhead, and relies on the underlying HTTP protocol for reliability.