The recommended spec is 4 cores and 6GB. Running this 24/7 for a year in US where the carbon intensity is about 400 gCO₂eq/kWh would produce about 150kg of CO2 per user per year. I appreciate the intent of this project, but it is not a sustainable approach. If you are taking a couple of pictures a day, you only need to run this service for a couple of minutes per day, the rest is wasted. With Google Photos, as a SaaS…
I'm not too comfortable pointing to the cloud providers for "efficiency", but you gotta go somewhere. I get that.
Personally I'm more a fan of building more efficient software (green software?). Using 6GB @ 4 cores to handle some media is a bit much IMO..