GTmetrix - GTmetrix is a free tool that analyzes your page's speed performance. Using PageSpeed and YSlow, GTmetrix generates scores for your pages and offers actionable recommendations on how to fix them.
Datadog - See metrics from all of your apps, tools & services in one place with Datadog's cloud monitoring as a service solution. Try it for free.
PageSpeed Insights - PageSpeed is addon for ...
AppDynamics - Get real-time insight from your apps using Application Performance Management—how they’re being used, how they’re performing, where they need help.
WebPagetest - Run a free website speed test from multiple locations around the globe using real browsers...
Zabbix - Track, record, alert and visualize performance and availability of IT resources