> But if your services are stateless, then you probably don't benefit at all from scaling them independently.

Quite easy to run into hardware, OS or especially language runtime (looking at you Ruby, Python) limitations when pushing even moderately high traffic even for totally stateless applications

I don't really understand what you mean by this or how it relates to what I said.

I certainly wasn't suggesting that you can vertically scale a service to handle unlimited traffic on a single instance.

The point is that if you have stateless services, where the resources being consumed per request are mainly CPU and network bandwidth, then "scaling independently" is not a useful thing to do. You can just scale everything instead of artificially restricting which instances can handle which kinds of requests.