At https://github.com/tbrand/which_is_the_fastest there’s comparison of the web frameworks.
It can give you a high level idea. And that is, Phoenix and Plug are slow compared to, for instance, Ruby and its framework Roda. Ruby/Roda is faster. Or at least roughly more or less the same as Phoenix and Plug.
I thought Phoenix and Plug would very well beat ruby and python with a magnitude of several times. But that’s not the case.
Why are Phoenix and Plug so slow?