> Any resources to learn more about how to roughly map traffic to number/type of instance, if that is what people do? Everything is going to depend on the spec

> Any resources to learn more about how to roughly map traffic to number/type of instance, if that is what people do? Everything is going to depend on the specific services and caching your application is going to run. Spin up an instance with the workload you want to test and run some benchmarks? It's free after all.