The development mode of New Relic (https://docs.newrelic.com/docs/agents/ruby-agent/developer-mode/developer-mode https://docs.newrelic.com/docs/agents/ruby-age

The development mode of New Relic (https://docs.newrelic.com/docs/agents/ruby-agent/developer-mode/developer-mode https://docs.newrelic.com/docs/agents/ruby-agent/developer-m...) is another good tool to find out about response times of your controller actions and the number of SQL queries. I'm pretty sure you can use it even if you're not on a paying plan for New Relic. We switched to this after we weren't been able to get rack-mini-profiler to work in a Rails app for a single-page app as the Rails app only returns JSON and doesn't render templates.