I wonder the opposite. Hardly any system needs to process 500k response per second. But nearly all of them benefit from the developer productivity that Python/Rails offer.
My current company has 15 Java & React engineers where 2 or 3 Rails would suffice. Load tops out at maybe a dozen requests/second. Feature development is super-slow. System complexity is off the charts.
> Feature development is super-slow. System complexity is off the charts.
That probably has little to do with language/stack and everything to do with constantly changing requirements/system growth.
To your required engineers comment, Spring Boot + jOOQ is easily one of the most productive backend stacks I've ever used. A single engineer could easily build a large API leveraging the stack.
Take a look a vert.x and Dropwizard. Spring Boot can handle maybe 10k requests per second, but Dropwizard is around 200k and vert.x maybe a million.
If you're only using them for a REST API they offer similar features. Spring Boot supports loads of other stuff you probably don't need for something API driven
I'm sure you'd need 10 or 15 bad Ruby developers as well. I've managed to kick things out the door very happily with one Java and one React developer before.
My current company has 15 Java & React engineers where 2 or 3 Rails would suffice. Load tops out at maybe a dozen requests/second. Feature development is super-slow. System complexity is off the charts.