Share Variables across multiple RPi

What would be your ideal approach to share global variables across multiple RPi's each with one node-red instance?

Would you take the approach of a MySQL database where you could write / read the variables?

I'd just use MQTT and persistent storage on each Pi


+1 for MQTT.

+2 for MQTT

+3 for MQTT.

If your unfamiliar with MQTT then this guide seems to be a good read;

thanks i will have a look at the guide and will be using mqtt