Mockoon is the easiest and quickest way to design and run mock REST APIs.

Datadog is a cloud-based monitoring and analytics platform that provides observability and security for cloud-scale applications

Burp or Burp Suite is a set of tools used for penetration testing of web applications. It is developed by a company named Portswigger who make freely available a Web Security Academy which has a range of lessons on penetration testing.

Browser and Mobile Automation Test Framework for Node.js

Status, performance and uptime monitoring for cron jobs, websites, APIs and more.

Meticulous monitors your daily interactions with your application as you develop it