This is a really great project and exactly what I was looking for as I have been interested in setting up something to monitor the levels of my kegs. I have several questions and concerns that I have listed below for your consideration:

1. It's possible to connect multiple scales by using an HX711 for each one, connecting each of those to the Arduino, and then adding a sensor for each in the weightsensor/config.json file to define the pins used, correct? I have 4 kegs that I would like to track, so I would have four scales and HX711 connected to various pin paris on the Arduino.
2. Is an Arduino Uno R3 mainboard sufficient?
3. The Arduino gets connected to the Raspberry Pi via USB and the Pi is running the weightsensor component?
4. Is a Raspberry Pi Zero W (1 Ghz single core, 512MB) sufficient?
5. Is it possible to run all of the components (weightsensor, weighthub, client) from the same Pi Zero?
6. How is scale drift due to temperature and constant weight load on the sensors being handled?
7. How often is the weight being sampled and sent to Firebase for storage? A very large concern is exceeding the free level of read/writes/data for Firebase and Firestore and getting billed for it. This concern increases as the number of kegs (currently 4) increases. Any information on how the measurement data is limited to prevent this would be appreciated.
8. Since it has been 2 years since the last update, is this project still being maintained? How has everything held up over time?

I look forward to your response. Thank you and keep up the great work!

Have you considered adding an option to use a Elasticsearch cluster with Kibana running locally rather than sending external to Google Firebase? Thanks!