This returns a Server-Timing header on all HTTP responses, which includes details on how long it took the server to render the response. Browsers can show this timing information in the devtools. In Chrome, go to the Network panel, then click a HTTP request, then click the Timing tab.
Environments
This directory contains environment-specific Rails configuration. This lets us have different configuration settings in development, test, and production modes.
Universal Rails configuration goes in config/application.rb or in config/initializers.