This is the correct answer, because the requirements for simplest and cheapest are met with CloudFunctions. CloudFunctions are for single purpose functions like image analysis. CloudFunctions also can be triggered by Cloud Storage events, so they provide seamless integration. The payment model based on number of requests, processing time of request (measured in 100ms units), and then other resources consumed is the most suitable of all options offered above. There is a free tier too. Cloud Functions also provides automatic scaling, high availability, and fault tolerance.