Comparison of MQTT and AMQP protocols with advantages and disadvantages of each and showcase of a proof of concept that combines the two for better reliability and efficiency.

1. MQTT meets AMQP
for reliable messaging
By Haci Murat Yaman 25/6/2023
https://www.linkedin.com/in/muratyaman/

2. MQTT: Message Queuing Telemetry Transport
“... lightweight messaging protocol designed for efficient communication between
devices in constrained networks”
It is a Pub/Sub protocol.
It is not a message queue.

3. MQTT: Advantages
● Lightweight and Efficient in terms of bandwidth & processing power
● Persistent Sessions:
○ Clients can maintain their subscriptions and message queues even if they temporarily disconnect from the
broker; this feature ensures message delivery to clients that were offline during a period of unreliable
connectivity. This is misleading!
● Publish/Subscribe Model:
○ Publishers send messages to a broker; subscribers receive messages from the broker.
● Asynchronous Communication:
○ The sender does not need to wait for an immediate response from the receiver.
● Quality of Service (QoS) Levels: This is very misleading!
○ 0 (At most once): Messages are delivered once but may be lost or duplicated.
○ 1 (At least once): Messages are guaranteed to be delivered at least once, but duplicates may occur.
○ 2 (Exactly once): Messages are ensured to be delivered exactly once by using a two-step handshake
process.
● Scalability and Flexibility: a broker handle many devices → suitable for IoT

4. MQTT: Disadvantages
● Increased Network Overhead:
○ esp. in extremely constrained networks or when dealing with a large number of small messages
● Lack of Built-in Security:
○ Even though it can work over TLS; MQTT applications should implement authentication.
● Potential Message Loss:
○ While higher QoS levels (such as QoS 1 and QoS 2) provide reliability, they can introduce additional
overhead and latency, impacting the overall efficiency of the communication.
● Lack of Standardized Support for Request-Response Communication:
○ Its pub/sub model is primarily designed for asynchronous communication.
● Limited Broker Features:
○ Brokers typically focus on message routing and delivery.
○ Advanced features like message persistence depends on implementation.
● Bandwidth Consumption:
○ In scenarios with extremely low-bandwidth or high-cost data connections, the continuous
transmission of MQTT control packets, keep-alive messages, and subscription updates can impact
the overall data consumption.

5. AMQP: Advanced Message Queuing Protocol
“... a messaging protocol that provides a reliable and flexible means of
communication between applications or components in a distributed system.”

6. AMQP: Advantages
● Reliable Message Delivery:
○ It uses acknowledgments and delivery confirmations.
● Interoperability:
○ It provides a standard way of exchanging messages
● Scalability:
○ It supports distributed and scalable messaging architectures.
○ We can add more instances of the message broker or message queues.
● Message Routing and Filtering:
○ It provides flexible mechanisms for routing messages such as header-based, topic-based, content-based.
● Security:
○ It includes built-in security features like authentication and authorization mechanisms
● Vendor Neutrality:
○ It is an open and standardized protocol.
● Message Persistence:
○ It supports durable message queues.
● Monitoring and Management:
○ It includes mechanisms for tracking message rates, queue sizes, and other metrics

7. AMQP: Disadvantages
● Complexity:
○ It can be complex to set up and configure.
○ Learning Curve for Developers: Effort is required to implement message producers and consumers correctly.
○ Operational Complexity: It requires configuring queues, setting up routing rules, monitoring message flows,
and ensuring high availability and fault tolerance.
● Performance Overhead:
○ Robustness and reliability features come with performance overhead; i.e. due to acknowledgments,
confirmations, and message persistence
● Protocol Compatibility:
○ Implementations of senders and receivers may not be compatible.
● Limited Real-Time Messaging:
○ Even though it is capable of handling real-time messaging, it may not be the optimal choice for extremely low-
latency, high-frequency messaging scenarios.
● Scalability Challenges:
○ Managing large-scale deployments with high message volumes requires careful planning, monitoring, and
load balancing to ensure efficient resource utilization and avoid bottlenecks.
● Potential Vendor Lock-In:
○ There is possibility of vendor lock-in if you heavily rely on proprietary extensions or features.

8. Devices are connected.
Network is stable.

9. Unstable network

10. Unstable network

11. Conclusion
The proof of concept works!
Code repository: https://github.com/muratyaman/mqtt-meets-amqp
But more testing is needed esp. under heavy load.
Could this stack of MQTT & AMQP work better than MQTT or AMQP alone?