The instrumentation has a performance overhead.

You enable the instrumentation with a prepend_before_action,

e.g.

prepend_around_action :callstacking_setup, if: -> { params[:debug] == '1' }

When the request is completed, the instrumented methods are removed (thus removing the overhead).

You have to enable it judiciously. But for a problematic request, it will give the entire team a holistic view as to what is really happening for a given request. What methods are called, their calling parameters, and return values, all are given visibility.

You no longer have to reconstruct production scenarios piecemeal via the rails console.