Protocol Fundamentals
MQTT and HTTP solve different communication problems in IoT architectures. Understanding their strengths helps you choose the right protocol for each use case.
MQTT
MQTT (Message Queuing Telemetry Transport) is a lightweight publish-subscribe protocol designed for constrained devices and unreliable networks.
Strengths:
Minimal overhead (~2 bytes header vs. HTTP's ~700+ bytes)
Persistent connections reduce reconnection cost
QoS levels (0, 1, 2) for delivery guarantees
Retained messages for last-known-good state
Will messages for device disconnect notification
Best for: Continuous telemetry, real-time monitoring, bidirectional device communication, resource-constrained devices.
HTTP/REST
HTTP is the universal web protocol. For IoT, it's used for device configuration, firmware downloads, and occasional data reporting.
Strengths:
Universal support - every device and framework speaks HTTP
Well-understood security model (HTTPS/TLS)
Caching and CDN support for firmware distribution
Request-response semantics match configuration operations
Best for: Device provisioning, firmware updates, configuration changes, low-frequency data reporting, integration with web services.
Head-to-Head
| Factor | MQTT | HTTP | |--------|------|------| | Latency | Low (persistent connection) | Higher (connection per request) | | Bandwidth | Very low | Higher (headers, cookies) | | Battery impact | Low | Higher | | Bidirectional | Native | Requires polling or WebSocket | | Reliability | QoS built-in | Application-level retry | | Scalability | Broker-dependent | Stateless, easy to scale |
The Hybrid Approach
Most production IoT architectures use both:
MQTT for telemetry and real-time control
HTTPS for firmware OTA, provisioning, and admin APIs
Conclusion
MQTT is the right default for device-to-cloud communication. HTTP supplements it for operations where request-response semantics and web infrastructure integration matter.