I'm using a pi to rebuild my temp capture platform, IFTTT just plain quit after the 0.9.xxx mc upgrades. Other than my issues posted elsewhere here, I am sending 'JSON" equivalent 'ListOfByte' successfully to my pi.
My plan is to use python libraries to captures the subscriptions and push them into PostgreSQL. It's all on my pi with a 128GB SSD. You might consider a middleman to push the data directly to a cloud hosted DB VS a cloud MQTT host and then to a DB.