Postman - The Collaboration Platform for API Development
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.
StopLight - Stoplight is an API Design, Development, and Documentation platform that enables consistency, reusability, and quality in your API lifecycle, all with an easy, enjoyable developer experience.
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.
Mockoon - Mock servers in seconds
Zabbix - Track, record, alert and visualize performance and availability of IT resources