IOT MQTT Message cost/billing appears larger than expected. Per character maybe?

Question

I deployed a prototype AWS FreeRTOS device in the field last week and my message count appears way out. By my count I received nearly 5000 messages over mqtt.
But according to my first bill that was 230,000 messages costing 23c - AWS IoT USW2-Messages.
Am I doing something wrong? Is the cost really per character maybe? My average message length is about 50.

Thanks in advance.

Accepted Answer

Hi. Messages are metered in 5KB increments.

> By my count I received nearly 5000 messages over mqtt.

Messages are metered in both directions, although PUBACKs are only metered when they are device to service. Details on metered messages here: https://aws.amazon.com/iot-core/pricing/additional-details/#MQTT_Message_Metering

Do you use other features, like shadows, that you perhaps aren't counting in the 5000?

You can use tools like [Protocol Metrics in CloudWatch](https://docs.aws.amazon.com/iot/latest/developerguide/metrics_dimensions.html#message-broker-metrics) to see more about the message activity. More information here:

https://docs.aws.amazon.com/iot/latest/developerguide/monitoring_overview.html

https://docs.aws.amazon.com/iot/latest/developerguide/metrics_dimensions.html

Answer

Thanks for the link. I found this there "MQTT PUBLISH (received from device)	Metered on the size of the payload and topic in bytes"
Marked as Solved.

IOT MQTT Message cost/billing appears larger than expected. Per character maybe?

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